Module java.base
Package java.lang

Class Class<T>

java.lang.Object
java.lang.Class<T>
Type Parameters:
T - the type of the class modeled by this Class object. For example, the type of String.class is Class<String>. Use Class<?> if the class being modeled is unknown.
All Implemented Interfaces:
Serializable, Constable, TypeDescriptor, TypeDescriptor.OfField<Class<?>>, AnnotatedElement, GenericDeclaration, Type
public final class Class<T>
extends Object
implements Serializable, GenericDeclaration, Type, AnnotatedElement, TypeDescriptor.OfField<Class<?>>, Constable
Instances of the class Class represent classes and interfaces in a running Java application. An enum type is a kind of class and an annotation type is a kind of interface. Every array also belongs to a class that is reflected as a Class object that is shared by all arrays with the same element type and number of dimensions. The primitive Java types (boolean, byte, char, short, int, long, float, and double), and the keyword void are also represented as Class objects.

Class has no public constructor. Instead a Class object is constructed automatically by the Java Virtual Machine when a class loader invokes one of the defineClass methods and passes the bytes of a class file.

The methods of class Class expose many characteristics of a class or interface. Most characteristics are derived from the class file that the class loader passed to the Java Virtual Machine. A few characteristics are determined by the class loading environment at run time, such as the module returned by getModule().

Some methods of class Class expose whether the declaration of a class or interface in Java source code was enclosed within another declaration. Other methods describe how a class or interface is situated in a nest. A nest is a set of classes and interfaces, in the same run-time package, that allow mutual access to their private members. The classes and interfaces are known as nestmates. One nestmate acts as the nest host, and enumerates the other nestmates which belong to the nest; each of them in turn records it as the nest host. The classes and interfaces which belong to a nest, including its host, are determined when class files are generated, for example, a Java compiler will typically record a top-level class as the host of a nest where the other members are the classes and interfaces whose declarations are enclosed within the top-level class declaration.

The following example uses a Class object to print the class name of an object: 

     void printClassName(Object obj) {
         System.out.println("The class of " + obj +
                            " is " + obj.getClass().getName());
     }

It is also possible to get the Class object for a named type (or for void) using a class literal. See Section 15.8.2 of The Java™ Language Specification. For example:

System.out.println("The name of class Foo is: "+Foo.class.getName());

Since:
1.0
See Also:
ClassLoader.defineClass(byte[], int, int), Serialized Form

  • Nested Class Summary

    Nested classes/interfaces declared in interface java.lang.invoke.TypeDescriptor

    TypeDescriptor.OfField<F extends TypeDescriptor.OfField<F>>, TypeDescriptor.OfMethod<F extends TypeDescriptor.OfField<F>,​M extends TypeDescriptor.OfMethod<F,​M>>

  • Method Summary

    Modifier and Type Method Description
    Class<?> arrayType()
    Returns a Class for an array type whose component type is described by this Class.
    <U> Class<? extends U> asSubclass​(Class<U> clazz)
    Casts this Class object to represent a subclass of the class represented by the specified class object.
    T cast​(Object obj)
    Casts an object to the class or interface represented by this Class object.
    Class<?> componentType()
    Returns the component type of this Class, if it describes an array type, or null otherwise.
    Optional<ClassDesc> describeConstable()
    Returns a nominal descriptor for this instance, if one can be constructed, or an empty Optional if one cannot be.
    String descriptorString()
    Returns the type descriptor string for this class.
    boolean desiredAssertionStatus()
    Returns the assertion status that would be assigned to this class if it were to be initialized at the time this method is invoked.
    static Class<?> forName​(Module module, String name)
    Returns the Class with the given binary name in the given module.
    static Class<?> forName​(String className)
    Returns the Class object associated with the class or interface with the given string name.
    static Class<?> forName​(String name, boolean initialize, ClassLoader loader)
    Returns the Class object associated with the class or interface with the given string name, using the given class loader.
    AnnotatedType[] getAnnotatedInterfaces()
    Returns an array of AnnotatedType objects that represent the use of types to specify superinterfaces of the entity represented by this Class object.
    AnnotatedType getAnnotatedSuperclass()
    Returns an AnnotatedType object that represents the use of a type to specify the superclass of the entity represented by this Class object.
    <A extends Annotation>
    A    		 getAnnotation​(Class<A> annotationClass)
    Returns this element's annotation for the specified type if such an annotation is present, else null.
    Annotation[] getAnnotations()
    Returns annotations that are present on this element.
    <A extends Annotation>
    A[]    		 getAnnotationsByType​(Class<A> annotationClass)
    Returns annotations that are associated with this element.
    String getCanonicalName()
    Returns the canonical name of the underlying class as defined by the Java Language Specification.
    Class<?>[] getClasses()
    Returns an array containing Class objects representing all the public classes and interfaces that are members of the class represented by this Class object.
    ClassLoader getClassLoader()
    Returns the class loader for the class.
    Class<?> getComponentType()
    Returns the Class representing the component type of an array.
    Constructor<T> getConstructor​(Class<?>... parameterTypes)
    Returns a Constructor object that reflects the specified public constructor of the class represented by this Class object.
    Constructor<?>[] getConstructors()
    Returns an array containing Constructor objects reflecting all the public constructors of the class represented by this Class object.
    <A extends Annotation>
    A    		 getDeclaredAnnotation​(Class<A> annotationClass)
    Returns this element's annotation for the specified type if such an annotation is directly present, else null.
    Annotation[] getDeclaredAnnotations()
    Returns annotations that are directly present on this element.
    <A extends Annotation>
    A[]    		 getDeclaredAnnotationsByType​(Class<A> annotationClass)
    Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present.
    Class<?>[] getDeclaredClasses()
    Returns an array of Class objects reflecting all the classes and interfaces declared as members of the class represented by this Class object.
    Constructor<T> getDeclaredConstructor​(Class<?>... parameterTypes)
    Returns a Constructor object that reflects the specified constructor of the class or interface represented by this Class object.
    Constructor<?>[] getDeclaredConstructors()
    Returns an array of Constructor objects reflecting all the constructors declared by the class represented by this Class object.
    Field getDeclaredField​(String name)
    Returns a Field object that reflects the specified declared field of the class or interface represented by this Class object.
    Field[] getDeclaredFields()
    Returns an array of Field objects reflecting all the fields declared by the class or interface represented by this Class object.
    Method getDeclaredMethod​(String name, Class<?>... parameterTypes)
    Returns a Method object that reflects the specified declared method of the class or interface represented by this Class object.
    Method[] getDeclaredMethods()
    Returns an array containing Method objects reflecting all the declared methods of the class or interface represented by this Class object, including public, protected, default (package) access, and private methods, but excluding inherited methods.
    Class<?> getDeclaringClass()
    If the class or interface represented by this Class object is a member of another class, returns the Class object representing the class in which it was declared.
    Class<?> getEnclosingClass()
    Returns the immediately enclosing class of the underlying class.
    Constructor<?> getEnclosingConstructor()
    If this Class object represents a local or anonymous class within a constructor, returns a Constructor object representing the immediately enclosing constructor of the underlying class.
    Method getEnclosingMethod()
    If this Class object represents a local or anonymous class within a method, returns a Method object representing the immediately enclosing method of the underlying class.
    T[] getEnumConstants()
    Returns the elements of this enum class or null if this Class object does not represent an enum type.
    Field getField​(String name)
    Returns a Field object that reflects the specified public member field of the class or interface represented by this Class object.
    Field[] getFields()
    Returns an array containing Field objects reflecting all the accessible public fields of the class or interface represented by this Class object.
    Type[] getGenericInterfaces()
    Returns the Types representing the interfaces directly implemented by the class or interface represented by this object.
    Type getGenericSuperclass()
    Returns the Type representing the direct superclass of the entity (class, interface, primitive type or void) represented by this Class.
    Class<?>[] getInterfaces()
    Returns the interfaces directly implemented by the class or interface represented by this object.
    Method getMethod​(String name, Class<?>... parameterTypes)
    Returns a Method object that reflects the specified public member method of the class or interface represented by this Class object.
    Method[] getMethods()
    Returns an array containing Method objects reflecting all the public methods of the class or interface represented by this Class object, including those declared by the class or interface and those inherited from superclasses and superinterfaces.
    int getModifiers()
    Returns the Java language modifiers for this class or interface, encoded in an integer.
    Module getModule()
    Returns the module that this class or interface is a member of.
    String getName()
    Returns the name of the entity (class, interface, array class, primitive type, or void) represented by this Class object, as a String.
    Class<?> getNestHost()
    Returns the nest host of the nest to which the class or interface represented by this Class object belongs.
    Class<?>[] getNestMembers()
    Returns an array containing Class objects representing all the classes and interfaces that are members of the nest to which the class or interface represented by this Class object belongs.
    Package getPackage()
    Gets the package of this class.
    String getPackageName()
    Returns the fully qualified package name.
    ProtectionDomain getProtectionDomain()
    Returns the ProtectionDomain of this class.
    URL getResource​(String name)
    Finds a resource with a given name.
    InputStream getResourceAsStream​(String name)
    Finds a resource with a given name.
    Object[] getSigners()
    Gets the signers of this class.
    String getSimpleName()
    Returns the simple name of the underlying class as given in the source code.
    Class<? super T> getSuperclass()
    Returns the Class representing the direct superclass of the entity (class, interface, primitive type or void) represented by this Class.
    String getTypeName()
    Return an informative string for the name of this type.
    TypeVariable<Class<T>>[] getTypeParameters()
    Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order.
    boolean isAnnotation()
    Returns true if this Class object represents an annotation type.
    boolean isAnnotationPresent​(Class<? extends Annotation> annotationClass)
    Returns true if an annotation for the specified type is present on this element, else false.
    boolean isAnonymousClass()
    Returns true if and only if the underlying class is an anonymous class.
    boolean isArray()
    Determines if this Class object represents an array class.
    boolean isAssignableFrom​(Class<?> cls)
    Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter.
    boolean isEnum()
    Returns true if and only if this class was declared as an enum in the source code.
    boolean isInstance​(Object obj)
    Determines if the specified Object is assignment-compatible with the object represented by this Class.
    boolean isInterface()
    Determines if the specified Class object represents an interface type.
    boolean isLocalClass()
    Returns true if and only if the underlying class is a local class.
    boolean isMemberClass()
    Returns true if and only if the underlying class is a member class.
    boolean isNestmateOf​(Class<?> c)
    Determines if the given Class is a nestmate of the class or interface represented by this Class object.
    boolean isPrimitive()
    Determines if the specified Class object represents a primitive type.
    boolean isSynthetic()
    Returns true if this class is a synthetic class; returns false otherwise.
    T newInstance()
    Deprecated.
    This method propagates any exception thrown by the nullary constructor, including a checked exception.
    String toGenericString()
    Returns a string describing this Class, including information about modifiers and type parameters.
    String toString()
    Converts the object to a string.

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

  • Method Details

    • toString

      public String toString()
      Converts the object to a string. The string representation is the string "class" or "interface", followed by a space, and then by the fully qualified name of the class in the format returned by getName. If this Class object represents a primitive type, this method returns the name of the primitive type. If this Class object represents void this method returns "void". If this Class object represents an array type, this method returns "class " followed by getName.
      Overrides:
      toString in class Object
      Returns:
      a string representation of this class object.

    • toGenericString

      public String toGenericString()
      Returns a string describing this Class, including information about modifiers and type parameters. The string is formatted as a list of type modifiers, if any, followed by the kind of type (empty string for primitive types and class, enum, interface, or @interface, as appropriate), followed by the type's name, followed by an angle-bracketed comma-separated list of the type's type parameters, if any, including informative bounds on the type parameters, if any. A space is used to separate modifiers from one another and to separate any modifiers from the kind of type. The modifiers occur in canonical order. If there are no type parameters, the type parameter list is elided. For an array type, the string starts with the type name, followed by an angle-bracketed comma-separated list of the type's type parameters, if any, followed by a sequence of [] characters, one set of brackets per dimension of the array.

      Note that since information about the runtime representation of a type is being generated, modifiers not present on the originating source code or illegal on the originating source code may be present.

      Returns:
      a string describing this Class, including information about modifiers and type parameters
      Since:
      1.8

    • forName

      public static Class<?> forName​(String className) throws ClassNotFoundException
      Returns the Class object associated with the class or interface with the given string name. Invoking this method is equivalent to:
      Class.forName(className, true, currentLoader)
      where currentLoader denotes the defining class loader of the current class.

      For example, the following code fragment returns the runtime Class descriptor for the class named java.lang.Thread:

      Class t = Class.forName("java.lang.Thread")

      A call to forName("X") causes the class named X to be initialized.

      Parameters:
      className - the fully qualified name of the desired class.
      Returns:
      the Class object for the class with the specified name.
      Throws:
      LinkageError - if the linkage fails
      ExceptionInInitializerError - if the initialization provoked by this method fails
      ClassNotFoundException - if the class cannot be located

    • forName

      public static Class<?> forName​(String name, boolean initialize, ClassLoader loader) throws ClassNotFoundException
      Returns the Class object associated with the class or interface with the given string name, using the given class loader. Given the fully qualified name for a class or interface (in the same format returned by getName) this method attempts to locate, load, and link the class or interface. The specified class loader is used to load the class or interface. If the parameter loader is null, the class is loaded through the bootstrap class loader. The class is initialized only if the initialize parameter is true and if it has not been initialized earlier.

      If name denotes a primitive type or void, an attempt will be made to locate a user-defined class in the unnamed package whose name is name. Therefore, this method cannot be used to obtain any of the Class objects representing primitive types or void.

      If name denotes an array class, the component type of the array class is loaded but not initialized.

      For example, in an instance method the expression:

      Class.forName("Foo")
      is equivalent to:
      Class.forName("Foo", true, this.getClass().getClassLoader())
      Note that this method throws errors related to loading, linking or initializing as specified in Sections 12.2, 12.3 and 12.4 of The Java Language Specification. Note that this method does not check whether the requested class is accessible to its caller.

      Parameters:
      name - fully qualified name of the desired class
      initialize - if true the class will be initialized. See Section 12.4 of The Java Language Specification.
      loader - class loader from which the class must be loaded
      Returns:
      class object representing the desired class
      Throws:
      LinkageError - if the linkage fails
      ExceptionInInitializerError - if the initialization provoked by this method fails
      ClassNotFoundException - if the class cannot be located by the specified class loader
      SecurityException - if a security manager is present, and the loader is null, and the caller's class loader is not null, and the caller does not have the RuntimePermission("getClassLoader")
      Since:
      1.2
      See Also:
      forName(String), ClassLoader

    • forName

      public static Class<?> forName​(Module module, String name)
      Returns the Class with the given binary name in the given module.

      This method attempts to locate, load, and link the class or interface. It does not run the class initializer. If the class is not found, this method returns null.

      If the class loader of the given module defines other modules and the given name is a class defined in a different module, this method returns null after the class is loaded.

      This method does not check whether the requested class is accessible to its caller.

      API Note:
      This method returns null on failure rather than throwing a ClassNotFoundException, as is done by the forName(String, boolean, ClassLoader) method. The security check is a stack-based permission check if the caller loads a class in another module.
      Parameters:
      module - A module
      name - The binary name of the class
      Returns:
      Class object of the given name defined in the given module; null if not found.
      Throws:
      NullPointerException - if the given module or name is null
      LinkageError - if the linkage fails
      SecurityException -
      • if the caller is not the specified module and RuntimePermission("getClassLoader") permission is denied; or
      • access to the module content is denied. For example, permission check will be performed when a class loader calls ModuleReader.open(String) to read the bytes of a class file in a module.
      Since:
      9

    • newInstance

      @Deprecated(since="9") public T newInstance() throws InstantiationException, IllegalAccessException
      Deprecated.
      This method propagates any exception thrown by the nullary constructor, including a checked exception. Use of this method effectively bypasses the compile-time exception checking that would otherwise be performed by the compiler. The Constructor.newInstance method avoids this problem by wrapping any exception thrown by the constructor in a (checked) InvocationTargetException.

      The call 

      
 clazz.newInstance()
      can be replaced by 
      
 clazz.getDeclaredConstructor().newInstance()
      The latter sequence of calls is inferred to be able to throw the additional exception types InvocationTargetException and NoSuchMethodException. Both of these exception types are subclasses of ReflectiveOperationException.

      Creates a new instance of the class represented by this Class object. The class is instantiated as if by a new expression with an empty argument list. The class is initialized if it has not already been initialized.
      Returns:
      a newly allocated instance of the class represented by this object.
      Throws:
      IllegalAccessException - if the class or its nullary constructor is not accessible.
      InstantiationException - if this Class represents an abstract class, an interface, an array class, a primitive type, or void; or if the class has no nullary constructor; or if the instantiation fails for some other reason.
      ExceptionInInitializerError - if the initialization provoked by this method fails.
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.

    • isInstance

      public boolean isInstance​(Object obj)
      Determines if the specified Object is assignment-compatible with the object represented by this Class. This method is the dynamic equivalent of the Java language instanceof operator. The method returns true if the specified Object argument is non-null and can be cast to the reference type represented by this Class object without raising a ClassCastException. It returns false otherwise.

      Specifically, if this Class object represents a declared class, this method returns true if the specified Object argument is an instance of the represented class (or of any of its subclasses); it returns false otherwise. If this Class object represents an array class, this method returns true if the specified Object argument can be converted to an object of the array class by an identity conversion or by a widening reference conversion; it returns false otherwise. If this Class object represents an interface, this method returns true if the class or any superclass of the specified Object argument implements this interface; it returns false otherwise. If this Class object represents a primitive type, this method returns false.

      Parameters:
      obj - the object to check
      Returns:
      true if obj is an instance of this class
      Since:
      1.1

    • isAssignableFrom

      public boolean isAssignableFrom​(Class<?> cls)
      Determines if the class or interface represented by this Class object is either the same as, or is a superclass or superinterface of, the class or interface represented by the specified Class parameter. It returns true if so; otherwise it returns false. If this Class object represents a primitive type, this method returns true if the specified Class parameter is exactly this Class object; otherwise it returns false.

      Specifically, this method tests whether the type represented by the specified Class parameter can be converted to the type represented by this Class object via an identity conversion or via a widening reference conversion. See The Java Language Specification, sections 5.1.1 and 5.1.4 , for details.

      Parameters:
      cls - the Class object to be checked
      Returns:
      the boolean value indicating whether objects of the type cls can be assigned to objects of this class
      Throws:
      NullPointerException - if the specified Class parameter is null.
      Since:
      1.1

    • isInterface

      public boolean isInterface()
      Determines if the specified Class object represents an interface type.
      Returns:
      true if this object represents an interface; false otherwise.

    • isArray

      public boolean isArray()
      Determines if this Class object represents an array class.
      Specified by:
      isArray in interface TypeDescriptor.OfField<T>
      Returns:
      true if this object represents an array class; false otherwise.
      Since:
      1.1

    • isPrimitive

      public boolean isPrimitive()
      Determines if the specified Class object represents a primitive type.

      There are nine predefined Class objects to represent the eight primitive types and void. These are created by the Java Virtual Machine, and have the same names as the primitive types that they represent, namely boolean, byte, char, short, int, long, float, and double.

      These objects may only be accessed via the following public static final variables, and are the only Class objects for which this method returns true.

      Specified by:
      isPrimitive in interface TypeDescriptor.OfField<T>
      Returns:
      true if and only if this class represents a primitive type
      Since:
      1.1
      See Also:
      Boolean.TYPE, Character.TYPE, Byte.TYPE, Short.TYPE, Integer.TYPE, Long.TYPE, Float.TYPE, Double.TYPE, Void.TYPE

    • isAnnotation

      public boolean isAnnotation()
      Returns true if this Class object represents an annotation type. Note that if this method returns true, isInterface() would also return true, as all annotation types are also interfaces.
      Returns:
      true if this class object represents an annotation type; false otherwise
      Since:
      1.5

    • isSynthetic

      public boolean isSynthetic()
      Returns true if this class is a synthetic class; returns false otherwise.
      Returns:
      true if and only if this class is a synthetic class as defined by the Java Language Specification.
      See Java Language Specification:
      13.1 The Form of a Binary
      Since:
      1.5

    • getName

      public String getName()
      Returns the name of the entity (class, interface, array class, primitive type, or void) represented by this Class object, as a String.

      If this class object represents a reference type that is not an array type then the binary name of the class is returned, as specified by The Java™ Language Specification.

      If this class object represents a primitive type or void, then the name returned is a String equal to the Java language keyword corresponding to the primitive type or void.

      If this class object represents a class of arrays, then the internal form of the name consists of the name of the element type preceded by one or more '[' characters representing the depth of the array nesting. The encoding of element type names is as follows:

      Element types and encodings
      Element Type Encoding
      boolean Z
      byte B
      char C
      class or interface Lclassname;
      double D
      float F
      int I
      long J
      short S

      The class or interface name classname is the binary name of the class specified above.

      Examples: 

       String.class.getName()
     returns "java.lang.String"
 byte.class.getName()
     returns "byte"
 (new Object[3]).getClass().getName()
     returns "[Ljava.lang.Object;"
 (new int[3][4][5][6][7][8][9]).getClass().getName()
     returns "[[[[[[[I"

      Returns:
      the name of the class or interface represented by this object.

    • getClassLoader

      public ClassLoader getClassLoader()
      Returns the class loader for the class. Some implementations may use null to represent the bootstrap class loader. This method will return null in such implementations if this class was loaded by the bootstrap class loader.

      If this object represents a primitive type or void, null is returned.

      Returns:
      the class loader that loaded the class or interface represented by this object.
      Throws:
      SecurityException - if a security manager is present, and the caller's class loader is not null and is not the same as or an ancestor of the class loader for the class whose class loader is requested, and the caller does not have the RuntimePermission("getClassLoader")
      See Also:
      ClassLoader, SecurityManager.checkPermission(java.security.Permission), RuntimePermission

    • getModule

      public Module getModule()
      Returns the module that this class or interface is a member of. If this class represents an array type then this method returns the Module for the element type. If this class represents a primitive type or void, then the Module object for the java.base module is returned. If this class is in an unnamed module then the unnamed Module of the class loader for this class is returned.
      Returns:
      the module that this class or interface is a member of
      Since:
      9

    • getTypeParameters

      public TypeVariable<Class<T>>[] getTypeParameters()
      Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order. Returns an array of length 0 if the underlying generic declaration declares no type variables.
      Specified by:
      getTypeParameters in interface GenericDeclaration
      Returns:
      an array of TypeVariable objects that represent the type variables declared by this generic declaration
      Throws:
      GenericSignatureFormatError - if the generic signature of this generic declaration does not conform to the format specified in The Java™ Virtual Machine Specification
      Since:
      1.5

    • getSuperclass

      public Class<? super T> getSuperclass()
      Returns the Class representing the direct superclass of the entity (class, interface, primitive type or void) represented by this Class. If this Class represents either the Object class, an interface, a primitive type, or void, then null is returned. If this object represents an array class then the Class object representing the Object class is returned.
      Returns:
      the direct superclass of the class represented by this object

    • getGenericSuperclass

      public Type getGenericSuperclass()
      Returns the Type representing the direct superclass of the entity (class, interface, primitive type or void) represented by this Class.

      If the superclass is a parameterized type, the Type object returned must accurately reflect the actual type arguments used in the source code. The parameterized type representing the superclass is created if it had not been created before. See the declaration of ParameterizedType for the semantics of the creation process for parameterized types. If this Class represents either the Object class, an interface, a primitive type, or void, then null is returned. If this object represents an array class then the Class object representing the Object class is returned.

      Returns:
      the direct superclass of the class represented by this object
      Throws:
      GenericSignatureFormatError - if the generic class signature does not conform to the format specified in The Java™ Virtual Machine Specification
      TypeNotPresentException - if the generic superclass refers to a non-existent type declaration
      MalformedParameterizedTypeException - if the generic superclass refers to a parameterized type that cannot be instantiated for any reason
      Since:
      1.5

    • getPackage

      public Package getPackage()
      Gets the package of this class.

      If this class represents an array type, a primitive type or void, this method returns null.

      Returns:
      the package of this class.

    • getPackageName

      public String getPackageName()
      Returns the fully qualified package name.

      If this class is a top level class, then this method returns the fully qualified name of the package that the class is a member of, or the empty string if the class is in an unnamed package.

      If this class is a member class, then this method is equivalent to invoking getPackageName() on the enclosing class.

      If this class is a local class or an anonymous class, then this method is equivalent to invoking getPackageName() on the declaring class of the enclosing method or enclosing constructor.

      If this class represents an array type then this method returns the package name of the element type. If this class represents a primitive type or void then the package name "java.lang" is returned.

      Returns:
      the fully qualified package name
      See Java Language Specification:
      6.7 Fully Qualified Names
      Since:
      9

    • getInterfaces

      public Class<?>[] getInterfaces()
      Returns the interfaces directly implemented by the class or interface represented by this object.

      If this object represents a class, the return value is an array containing objects representing all interfaces directly implemented by the class. The order of the interface objects in the array corresponds to the order of the interface names in the implements clause of the declaration of the class represented by this object. For example, given the declaration:

      class Shimmer implements FloorWax, DessertTopping { ... }
      suppose the value of s is an instance of Shimmer; the value of the expression:
      s.getClass().getInterfaces()[0]
      is the Class object that represents interface FloorWax; and the value of:
      s.getClass().getInterfaces()[1]
      is the Class object that represents interface DessertTopping.

      If this object represents an interface, the array contains objects representing all interfaces directly extended by the interface. The order of the interface objects in the array corresponds to the order of the interface names in the extends clause of the declaration of the interface represented by this object.

      If this object represents a class or interface that implements no interfaces, the method returns an array of length 0.

      If this object represents a primitive type or void, the method returns an array of length 0.

      If this Class object represents an array type, the interfaces Cloneable and java.io.Serializable are returned in that order.

      Returns:
      an array of interfaces directly implemented by this class

    • getGenericInterfaces

      public Type[] getGenericInterfaces()
      Returns the Types representing the interfaces directly implemented by the class or interface represented by this object.

      If a superinterface is a parameterized type, the Type object returned for it must accurately reflect the actual type arguments used in the source code. The parameterized type representing each superinterface is created if it had not been created before. See the declaration of ParameterizedType for the semantics of the creation process for parameterized types.

      If this object represents a class, the return value is an array containing objects representing all interfaces directly implemented by the class. The order of the interface objects in the array corresponds to the order of the interface names in the implements clause of the declaration of the class represented by this object.

      If this object represents an interface, the array contains objects representing all interfaces directly extended by the interface. The order of the interface objects in the array corresponds to the order of the interface names in the extends clause of the declaration of the interface represented by this object.

      If this object represents a class or interface that implements no interfaces, the method returns an array of length 0.

      If this object represents a primitive type or void, the method returns an array of length 0.

      If this Class object represents an array type, the interfaces Cloneable and java.io.Serializable are returned in that order.

      Returns:
      an array of interfaces directly implemented by this class
      Throws:
      GenericSignatureFormatError - if the generic class signature does not conform to the format specified in The Java™ Virtual Machine Specification
      TypeNotPresentException - if any of the generic superinterfaces refers to a non-existent type declaration
      MalformedParameterizedTypeException - if any of the generic superinterfaces refer to a parameterized type that cannot be instantiated for any reason
      Since:
      1.5

    • getComponentType

      public Class<?> getComponentType()
      Returns the Class representing the component type of an array. If this class does not represent an array class this method returns null.
      Returns:
      the Class representing the component type of this class if this class is an array
      Since:
      1.1
      See Also:
      Array

    • getModifiers

      public int getModifiers()
      Returns the Java language modifiers for this class or interface, encoded in an integer. The modifiers consist of the Java Virtual Machine's constants for public, protected, private, final, static, abstract and interface; they should be decoded using the methods of class Modifier.

      If the underlying class is an array class, then its public, private and protected modifiers are the same as those of its component type. If this Class represents a primitive type or void, its public modifier is always true, and its protected and private modifiers are always false. If this object represents an array class, a primitive type or void, then its final modifier is always true and its interface modifier is always false. The values of its other modifiers are not determined by this specification.

      The modifier encodings are defined in The Java Virtual Machine Specification, table 4.1.

      Returns:
      the int representing the modifiers for this class
      Since:
      1.1
      See Also:
      Modifier

    • getSigners

      public Object[] getSigners()
      Gets the signers of this class.
      Returns:
      the signers of this class, or null if there are no signers. In particular, this method returns null if this object represents a primitive type or void.
      Since:
      1.1

    • getEnclosingMethod

      public Method getEnclosingMethod() throws SecurityException
      If this Class object represents a local or anonymous class within a method, returns a Method object representing the immediately enclosing method of the underlying class. Returns null otherwise. In particular, this method returns null if the underlying class is a local or anonymous class immediately enclosed by a type declaration, instance initializer or static initializer.
      Returns:
      the immediately enclosing method of the underlying class, if that class is a local or anonymous class; otherwise null.
      Throws:
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of the enclosing class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the methods within the enclosing class
      • the caller's class loader is not the same as or an ancestor of the class loader for the enclosing class and invocation of s.checkPackageAccess() denies access to the package of the enclosing class
      Since:
      1.5

    • getEnclosingConstructor

      public Constructor<?> getEnclosingConstructor() throws SecurityException
      If this Class object represents a local or anonymous class within a constructor, returns a Constructor object representing the immediately enclosing constructor of the underlying class. Returns null otherwise. In particular, this method returns null if the underlying class is a local or anonymous class immediately enclosed by a type declaration, instance initializer or static initializer.
      Returns:
      the immediately enclosing constructor of the underlying class, if that class is a local or anonymous class; otherwise null.
      Throws:
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of the enclosing class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the constructors within the enclosing class
      • the caller's class loader is not the same as or an ancestor of the class loader for the enclosing class and invocation of s.checkPackageAccess() denies access to the package of the enclosing class
      Since:
      1.5

    • getDeclaringClass

      public Class<?> getDeclaringClass() throws SecurityException
      If the class or interface represented by this Class object is a member of another class, returns the Class object representing the class in which it was declared. This method returns null if this class or interface is not a member of any other class. If this Class object represents an array class, a primitive type, or void,then this method returns null.
      Returns:
      the declaring class for this class
      Throws:
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the declaring class and invocation of s.checkPackageAccess() denies access to the package of the declaring class
      Since:
      1.1

    • getEnclosingClass

      public Class<?> getEnclosingClass() throws SecurityException
      Returns the immediately enclosing class of the underlying class. If the underlying class is a top level class this method returns null.
      Returns:
      the immediately enclosing class of the underlying class
      Throws:
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the enclosing class and invocation of s.checkPackageAccess() denies access to the package of the enclosing class
      Since:
      1.5

    • getSimpleName

      public String getSimpleName()
      Returns the simple name of the underlying class as given in the source code. Returns an empty string if the underlying class is anonymous.

      The simple name of an array is the simple name of the component type with "[]" appended. In particular the simple name of an array whose component type is anonymous is "[]".

      Returns:
      the simple name of the underlying class
      Since:
      1.5

    • getTypeName

      public String getTypeName()
      Return an informative string for the name of this type.
      Specified by:
      getTypeName in interface Type
      Returns:
      an informative string for the name of this type
      Since:
      1.8

    • getCanonicalName

      public String getCanonicalName()
      Returns the canonical name of the underlying class as defined by the Java Language Specification. Returns null if the underlying class does not have a canonical name (i.e., if it is a local or anonymous class or an array whose component type does not have a canonical name).
      Returns:
      the canonical name of the underlying class if it exists, and null otherwise.
      Since:
      1.5

    • isAnonymousClass

      public boolean isAnonymousClass()
      Returns true if and only if the underlying class is an anonymous class.
      Returns:
      true if and only if this class is an anonymous class.
      Since:
      1.5

    • isLocalClass

      public boolean isLocalClass()
      Returns true if and only if the underlying class is a local class.
      Returns:
      true if and only if this class is a local class.
      Since:
      1.5

    • isMemberClass

      public boolean isMemberClass()
      Returns true if and only if the underlying class is a member class.
      Returns:
      true if and only if this class is a member class.
      Since:
      1.5

    • getClasses

      public Class<?>[] getClasses()
      Returns an array containing Class objects representing all the public classes and interfaces that are members of the class represented by this Class object. This includes public class and interface members inherited from superclasses and public class and interface members declared by the class. This method returns an array of length 0 if this Class object has no public member classes or interfaces. This method also returns an array of length 0 if this Class object represents a primitive type, an array class, or void.
      Returns:
      the array of Class objects representing the public members of this class
      Throws:
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      Since:
      1.1

    • getFields

      public Field[] getFields() throws SecurityException
      Returns an array containing Field objects reflecting all the accessible public fields of the class or interface represented by this Class object.

      If this Class object represents a class or interface with no accessible public fields, then this method returns an array of length 0.

      If this Class object represents a class, then this method returns the public fields of the class and of all its superclasses and superinterfaces.

      If this Class object represents an interface, then this method returns the fields of the interface and of all its superinterfaces.

      If this Class object represents an array type, a primitive type, or void, then this method returns an array of length 0.

      The elements in the returned array are not sorted and are not in any particular order.

      Returns:
      the array of Field objects representing the public fields
      Throws:
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      See Java Language Specification:
      8.2 Class Members
      8.3 Field Declarations
      Since:
      1.1

    • getMethods

      public Method[] getMethods() throws SecurityException
      Returns an array containing Method objects reflecting all the public methods of the class or interface represented by this Class object, including those declared by the class or interface and those inherited from superclasses and superinterfaces.

      If this Class object represents an array type, then the returned array has a Method object for each of the public methods inherited by the array type from Object. It does not contain a Method object for clone().

      If this Class object represents an interface then the returned array does not contain any implicitly declared methods from Object. Therefore, if no methods are explicitly declared in this interface or any of its superinterfaces then the returned array has length 0. (Note that a Class object which represents a class always has public methods, inherited from Object.)

      The returned array never contains methods with names "<init>" or "<clinit>".

      The elements in the returned array are not sorted and are not in any particular order.

      Generally, the result is computed as with the following 4 step algorithm. Let C be the class or interface represented by this Class object:

      1. A union of methods is composed of:
        1. C's declared public instance and static methods as returned by getDeclaredMethods() and filtered to include only public methods.
        2. If C is a class other than Object, then include the result of invoking this algorithm recursively on the superclass of C.
        3. Include the results of invoking this algorithm recursively on all direct superinterfaces of C, but include only instance methods.
      2. Union from step 1 is partitioned into subsets of methods with same signature (name, parameter types) and return type.
      3. Within each such subset only the most specific methods are selected. Let method M be a method from a set of methods with same signature and return type. M is most specific if there is no such method N != M from the same set, such that N is more specific than M. N is more specific than M if:
        1. N is declared by a class and M is declared by an interface; or
        2. N and M are both declared by classes or both by interfaces and N's declaring type is the same as or a subtype of M's declaring type (clearly, if M's and N's declaring types are the same type, then M and N are the same method).
      4. The result of this algorithm is the union of all selected methods from step 3.

      API Note:
      There may be more than one method with a particular name and parameter types in a class because while the Java language forbids a class to declare multiple methods with the same signature but different return types, the Java virtual machine does not. This increased flexibility in the virtual machine can be used to implement various language features. For example, covariant returns can be implemented with bridge methods; the bridge method and the overriding method would have the same signature but different return types.
      Returns:
      the array of Method objects representing the public methods of this class
      Throws:
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      See Java Language Specification:
      8.2 Class Members
      8.4 Method Declarations
      Since:
      1.1

    • getConstructors

      public Constructor<?>[] getConstructors() throws SecurityException
      Returns an array containing Constructor objects reflecting all the public constructors of the class represented by this Class object. An array of length 0 is returned if the class has no public constructors, or if the class is an array class, or if the class reflects a primitive type or void. Note that while this method returns an array of Constructor<T> objects (that is an array of constructors from this class), the return type of this method is Constructor<?>[] and not Constructor<T>[] as might be expected. This less informative return type is necessary since after being returned from this method, the array could be modified to hold Constructor objects for different classes, which would violate the type guarantees of Constructor<T>[].
      Returns:
      the array of Constructor objects representing the public constructors of this class
      Throws:
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      Since:
      1.1

    • getField

      public Field getField​(String name) throws NoSuchFieldException, SecurityException
      Returns a Field object that reflects the specified public member field of the class or interface represented by this Class object. The name parameter is a String specifying the simple name of the desired field.

      The field to be reflected is determined by the algorithm that follows. Let C be the class or interface represented by this object:

      1. If C declares a public field with the name specified, that is the field to be reflected.
      2. If no field was found in step 1 above, this algorithm is applied recursively to each direct superinterface of C. The direct superinterfaces are searched in the order they were declared.
      3. If no field was found in steps 1 and 2 above, and C has a superclass S, then this algorithm is invoked recursively upon S. If C has no superclass, then a NoSuchFieldException is thrown.

      If this Class object represents an array type, then this method does not find the length field of the array type.

      Parameters:
      name - the field name
      Returns:
      the Field object of this class specified by name
      Throws:
      NoSuchFieldException - if a field with the specified name is not found.
      NullPointerException - if name is null
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      See Java Language Specification:
      8.2 Class Members
      8.3 Field Declarations
      Since:
      1.1

    • getMethod

      public Method getMethod​(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
      Returns a Method object that reflects the specified public member method of the class or interface represented by this Class object. The name parameter is a String specifying the simple name of the desired method. The parameterTypes parameter is an array of Class objects that identify the method's formal parameter types, in declared order. If parameterTypes is null, it is treated as if it were an empty array.

      If this Class object represents an array type, then this method finds any public method inherited by the array type from Object except method clone().

      If this Class object represents an interface then this method does not find any implicitly declared method from Object. Therefore, if no methods are explicitly declared in this interface or any of its superinterfaces, then this method does not find any method.

      This method does not find any method with name "<init>" or "<clinit>".

      Generally, the method to be reflected is determined by the 4 step algorithm that follows. Let C be the class or interface represented by this Class object:

      1. A union of methods is composed of:
        1. C's declared public instance and static methods as returned by getDeclaredMethods() and filtered to include only public methods that match given name and parameterTypes
        2. If C is a class other than Object, then include the result of invoking this algorithm recursively on the superclass of C.
        3. Include the results of invoking this algorithm recursively on all direct superinterfaces of C, but include only instance methods.
      2. This union is partitioned into subsets of methods with same return type (the selection of methods from step 1 also guarantees that they have the same method name and parameter types).
      3. Within each such subset only the most specific methods are selected. Let method M be a method from a set of methods with same VM signature (return type, name, parameter types). M is most specific if there is no such method N != M from the same set, such that N is more specific than M. N is more specific than M if:
        1. N is declared by a class and M is declared by an interface; or
        2. N and M are both declared by classes or both by interfaces and N's declaring type is the same as or a subtype of M's declaring type (clearly, if M's and N's declaring types are the same type, then M and N are the same method).
      4. The result of this algorithm is chosen arbitrarily from the methods with most specific return type among all selected methods from step 3. Let R be a return type of a method M from the set of all selected methods from step 3. M is a method with most specific return type if there is no such method N != M from the same set, having return type S != R, such that S is a subtype of R as determined by R.class.isAssignableFrom(java.lang.Class<?>)(S.class).

      API Note:
      There may be more than one method with matching name and parameter types in a class because while the Java language forbids a class to declare multiple methods with the same signature but different return types, the Java virtual machine does not. This increased flexibility in the virtual machine can be used to implement various language features. For example, covariant returns can be implemented with bridge methods; the bridge method and the overriding method would have the same signature but different return types. This method would return the overriding method as it would have a more specific return type.
      Parameters:
      name - the name of the method
      parameterTypes - the list of parameters
      Returns:
      the Method object that matches the specified name and parameterTypes
      Throws:
      NoSuchMethodException - if a matching method is not found or if the name is "<init>"or "<clinit>".
      NullPointerException - if name is null
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      See Java Language Specification:
      8.2 Class Members
      8.4 Method Declarations
      Since:
      1.1

    • getConstructor

      public Constructor<T> getConstructor​(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
      Returns a Constructor object that reflects the specified public constructor of the class represented by this Class object. The parameterTypes parameter is an array of Class objects that identify the constructor's formal parameter types, in declared order. If this Class object represents an inner class declared in a non-static context, the formal parameter types include the explicit enclosing instance as the first parameter.

      The constructor to reflect is the public constructor of the class represented by this Class object whose formal parameter types match those specified by parameterTypes.

      Parameters:
      parameterTypes - the parameter array
      Returns:
      the Constructor object of the public constructor that matches the specified parameterTypes
      Throws:
      NoSuchMethodException - if a matching method is not found.
      SecurityException - If a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class.
      Since:
      1.1

    • getDeclaredClasses

      public Class<?>[] getDeclaredClasses() throws SecurityException
      Returns an array of Class objects reflecting all the classes and interfaces declared as members of the class represented by this Class object. This includes public, protected, default (package) access, and private classes and interfaces declared by the class, but excludes inherited classes and interfaces. This method returns an array of length 0 if the class declares no classes or interfaces as members, or if this Class object represents a primitive type, an array class, or void.
      Returns:
      the array of Class objects representing all the declared members of this class
      Throws:
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared classes within this class
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      Since:
      1.1

    • getDeclaredFields

      public Field[] getDeclaredFields() throws SecurityException
      Returns an array of Field objects reflecting all the fields declared by the class or interface represented by this Class object. This includes public, protected, default (package) access, and private fields, but excludes inherited fields.

      If this Class object represents a class or interface with no declared fields, then this method returns an array of length 0.

      If this Class object represents an array type, a primitive type, or void, then this method returns an array of length 0.

      The elements in the returned array are not sorted and are not in any particular order.

      Returns:
      the array of Field objects representing all the declared fields of this class
      Throws:
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared fields within this class
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      See Java Language Specification:
      8.2 Class Members
      8.3 Field Declarations
      Since:
      1.1

    • getDeclaredMethods

      public Method[] getDeclaredMethods() throws SecurityException
      Returns an array containing Method objects reflecting all the declared methods of the class or interface represented by this Class object, including public, protected, default (package) access, and private methods, but excluding inherited methods.

      If this Class object represents a type that has multiple declared methods with the same name and parameter types, but different return types, then the returned array has a Method object for each such method.

      If this Class object represents a type that has a class initialization method <clinit>, then the returned array does not have a corresponding Method object.

      If this Class object represents a class or interface with no declared methods, then the returned array has length 0.

      If this Class object represents an array type, a primitive type, or void, then the returned array has length 0.

      The elements in the returned array are not sorted and are not in any particular order.

      Returns:
      the array of Method objects representing all the declared methods of this class
      Throws:
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared methods within this class
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      See Java Language Specification:
      8.2 Class Members
      8.4 Method Declarations
      Since:
      1.1

    • getDeclaredConstructors

      public Constructor<?>[] getDeclaredConstructors() throws SecurityException
      Returns an array of Constructor objects reflecting all the constructors declared by the class represented by this Class object. These are public, protected, default (package) access, and private constructors. The elements in the array returned are not sorted and are not in any particular order. If the class has a default constructor, it is included in the returned array. This method returns an array of length 0 if this Class object represents an interface, a primitive type, an array class, or void.

      See The Java Language Specification, section 8.2.

      Returns:
      the array of Constructor objects representing all the declared constructors of this class
      Throws:
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared constructors within this class
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      Since:
      1.1

    • getDeclaredField

      public Field getDeclaredField​(String name) throws NoSuchFieldException, SecurityException
      Returns a Field object that reflects the specified declared field of the class or interface represented by this Class object. The name parameter is a String that specifies the simple name of the desired field.

      If this Class object represents an array type, then this method does not find the length field of the array type.

      Parameters:
      name - the name of the field
      Returns:
      the Field object for the specified field in this class
      Throws:
      NoSuchFieldException - if a field with the specified name is not found.
      NullPointerException - if name is null
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared field
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      See Java Language Specification:
      8.2 Class Members
      8.3 Field Declarations
      Since:
      1.1

    • getDeclaredMethod

      public Method getDeclaredMethod​(String name, Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
      Returns a Method object that reflects the specified declared method of the class or interface represented by this Class object. The name parameter is a String that specifies the simple name of the desired method, and the parameterTypes parameter is an array of Class objects that identify the method's formal parameter types, in declared order. If more than one method with the same parameter types is declared in a class, and one of these methods has a return type that is more specific than any of the others, that method is returned; otherwise one of the methods is chosen arbitrarily. If the name is "<init>"or "<clinit>" a NoSuchMethodException is raised.

      If this Class object represents an array type, then this method does not find the clone() method.

      Parameters:
      name - the name of the method
      parameterTypes - the parameter array
      Returns:
      the Method object for the method of this class matching the specified name and parameters
      Throws:
      NoSuchMethodException - if a matching method is not found.
      NullPointerException - if name is null
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared method
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      See Java Language Specification:
      8.2 Class Members
      8.4 Method Declarations
      Since:
      1.1

    • getDeclaredConstructor

      public Constructor<T> getDeclaredConstructor​(Class<?>... parameterTypes) throws NoSuchMethodException, SecurityException
      Returns a Constructor object that reflects the specified constructor of the class or interface represented by this Class object. The parameterTypes parameter is an array of Class objects that identify the constructor's formal parameter types, in declared order. If this Class object represents an inner class declared in a non-static context, the formal parameter types include the explicit enclosing instance as the first parameter.
      Parameters:
      parameterTypes - the parameter array
      Returns:
      The Constructor object for the constructor with the specified parameter list
      Throws:
      NoSuchMethodException - if a matching method is not found.
      SecurityException - If a security manager, s, is present and any of the following conditions is met:
      • the caller's class loader is not the same as the class loader of this class and invocation of s.checkPermission method with RuntimePermission("accessDeclaredMembers") denies access to the declared constructor
      • the caller's class loader is not the same as or an ancestor of the class loader for the current class and invocation of s.checkPackageAccess() denies access to the package of this class
      Since:
      1.1

    • getResourceAsStream

      public InputStream getResourceAsStream​(String name)
      Finds a resource with a given name.

      If this class is in a named Module then this method will attempt to find the resource in the module. This is done by delegating to the module's class loader findResource(String,String) method, invoking it with the module name and the absolute name of the resource. Resources in named modules are subject to the rules for encapsulation specified in the Module getResourceAsStream method and so this method returns null when the resource is a non-".class" resource in a package that is not open to the caller's module.

      Otherwise, if this class is not in a named module then the rules for searching resources associated with a given class are implemented by the defining class loader of the class. This method delegates to this object's class loader. If this object was loaded by the bootstrap class loader, the method delegates to ClassLoader.getSystemResourceAsStream(java.lang.String).

      Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:

      • If the name begins with a '/' ('\u002f'), then the absolute name of the resource is the portion of the name following the '/'.
      • Otherwise, the absolute name is of the following form:
        modified_package_name/name

        Where the modified_package_name is the package name of this object with '/' substituted for '.' ('\u002e').

      Parameters:
      name - name of the desired resource
      Returns:
      A InputStream object; null if no resource with this name is found, the resource is in a package that is not open to at least the caller module, or access to the resource is denied by the security manager.
      Throws:
      NullPointerException - If name is null
      Since:
      1.1
      See Also:
      Module.getResourceAsStream(String)

    • getResource

      public URL getResource​(String name)
      Finds a resource with a given name.

      If this class is in a named Module then this method will attempt to find the resource in the module. This is done by delegating to the module's class loader findResource(String,String) method, invoking it with the module name and the absolute name of the resource. Resources in named modules are subject to the rules for encapsulation specified in the Module getResourceAsStream method and so this method returns null when the resource is a non-".class" resource in a package that is not open to the caller's module.

      Otherwise, if this class is not in a named module then the rules for searching resources associated with a given class are implemented by the defining class loader of the class. This method delegates to this object's class loader. If this object was loaded by the bootstrap class loader, the method delegates to ClassLoader.getSystemResource(java.lang.String).

      Before delegation, an absolute resource name is constructed from the given resource name using this algorithm:

      • If the name begins with a '/' ('\u002f'), then the absolute name of the resource is the portion of the name following the '/'.
      • Otherwise, the absolute name is of the following form:
        modified_package_name/name

        Where the modified_package_name is the package name of this object with '/' substituted for '.' ('\u002e').

      Parameters:
      name - name of the desired resource
      Returns:
      A URL object; null if no resource with this name is found, the resource cannot be located by a URL, the resource is in a package that is not open to at least the caller module, or access to the resource is denied by the security manager.
      Throws:
      NullPointerException - If name is null
      Since:
      1.1

    • getProtectionDomain

      public ProtectionDomain getProtectionDomain()
      Returns the ProtectionDomain of this class. If there is a security manager installed, this method first calls the security manager's checkPermission method with a RuntimePermission("getProtectionDomain") permission to ensure it's ok to get the ProtectionDomain.
      Returns:
      the ProtectionDomain of this class
      Throws:
      SecurityException - if a security manager exists and its checkPermission method doesn't allow getting the ProtectionDomain.
      Since:
      1.2
      See Also:
      ProtectionDomain, SecurityManager.checkPermission(java.security.Permission), RuntimePermission

    • desiredAssertionStatus

      public boolean desiredAssertionStatus()
      Returns the assertion status that would be assigned to this class if it were to be initialized at the time this method is invoked. If this class has had its assertion status set, the most recent setting will be returned; otherwise, if any package default assertion status pertains to this class, the most recent setting for the most specific pertinent package default assertion status is returned; otherwise, if this class is not a system class (i.e., it has a class loader) its class loader's default assertion status is returned; otherwise, the system class default assertion status is returned.

      Few programmers will have any need for this method; it is provided for the benefit of the JRE itself. (It allows a class to determine at the time that it is initialized whether assertions should be enabled.) Note that this method is not guaranteed to return the actual assertion status that was (or will be) associated with the specified class when it was (or will be) initialized.

      Returns:
      the desired assertion status of the specified class.
      Since:
      1.4
      See Also:
      ClassLoader.setClassAssertionStatus(java.lang.String, boolean), ClassLoader.setPackageAssertionStatus(java.lang.String, boolean), ClassLoader.setDefaultAssertionStatus(boolean)

    • isEnum

      public boolean isEnum()
      Returns true if and only if this class was declared as an enum in the source code.
      Returns:
      true if and only if this class was declared as an enum in the source code
      Since:
      1.5

    • getEnumConstants

      public T[] getEnumConstants()
      Returns the elements of this enum class or null if this Class object does not represent an enum type.
      Returns:
      an array containing the values comprising the enum class represented by this Class object in the order they're declared, or null if this Class object does not represent an enum type
      Since:
      1.5

    • cast

      public T cast​(Object obj)
      Casts an object to the class or interface represented by this Class object.
      Parameters:
      obj - the object to be cast
      Returns:
      the object after casting, or null if obj is null
      Throws:
      ClassCastException - if the object is not null and is not assignable to the type T.
      Since:
      1.5

    • asSubclass

      public <U> Class<? extends U> asSubclass​(Class<U> clazz)
      Casts this Class object to represent a subclass of the class represented by the specified class object. Checks that the cast is valid, and throws a ClassCastException if it is not. If this method succeeds, it always returns a reference to this class object.

      This method is useful when a client needs to "narrow" the type of a Class object to pass it to an API that restricts the Class objects that it is willing to accept. A cast would generate a compile-time warning, as the correctness of the cast could not be checked at runtime (because generic types are implemented by erasure).

      Type Parameters:
      U - the type to cast this class object to
      Parameters:
      clazz - the class of the type to cast this class object to
      Returns:
      this Class object, cast to represent a subclass of the specified class object.
      Throws:
      ClassCastException - if this Class object does not represent a subclass of the specified class (here "subclass" includes the class itself).
      Since:
      1.5

    • getAnnotation

      public <A extends Annotation> A getAnnotation​(Class<A> annotationClass)
      Description copied from interface: AnnotatedElement
      Returns this element's annotation for the specified type if such an annotation is present, else null.
      Specified by:
      getAnnotation in interface AnnotatedElement
      Type Parameters:
      A - the type of the annotation to query for and return if present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      this element's annotation for the specified annotation type if present on this element, else null
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.5

    • isAnnotationPresent

      public boolean isAnnotationPresent​(Class<? extends Annotation> annotationClass)
      Returns true if an annotation for the specified type is present on this element, else false. This method is designed primarily for convenient access to marker annotations.

      The truth value returned by this method is equivalent to: getAnnotation(annotationClass) != null

      The body of the default method is specified to be the code above.

      Specified by:
      isAnnotationPresent in interface AnnotatedElement
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      true if an annotation for the specified annotation type is present on this element, else false
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.5

    • getAnnotationsByType

      public <A extends Annotation> A[] getAnnotationsByType​(Class<A> annotationClass)
      Description copied from interface: AnnotatedElement
      Returns annotations that are associated with this element. If there are no annotations associated with this element, the return value is an array of length 0. The difference between this method and AnnotatedElement.getAnnotation(Class) is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
      Specified by:
      getAnnotationsByType in interface AnnotatedElement
      Type Parameters:
      A - the type of the annotation to query for and return if present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      all this element's annotations for the specified annotation type if associated with this element, else an array of length zero
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.8

    • getAnnotations

      public Annotation[] getAnnotations()
      Description copied from interface: AnnotatedElement
      Returns annotations that are present on this element. If there are no annotations present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
      Specified by:
      getAnnotations in interface AnnotatedElement
      Returns:
      annotations present on this element
      Since:
      1.5

    • getDeclaredAnnotation

      public <A extends Annotation> A getDeclaredAnnotation​(Class<A> annotationClass)
      Description copied from interface: AnnotatedElement
      Returns this element's annotation for the specified type if such an annotation is directly present, else null. This method ignores inherited annotations. (Returns null if no annotations are directly present on this element.)
      Specified by:
      getDeclaredAnnotation in interface AnnotatedElement
      Type Parameters:
      A - the type of the annotation to query for and return if directly present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      this element's annotation for the specified annotation type if directly present on this element, else null
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.8

    • getDeclaredAnnotationsByType

      public <A extends Annotation> A[] getDeclaredAnnotationsByType​(Class<A> annotationClass)
      Description copied from interface: AnnotatedElement
      Returns this element's annotation(s) for the specified type if such annotations are either directly present or indirectly present. This method ignores inherited annotations. If there are no specified annotations directly or indirectly present on this element, the return value is an array of length 0. The difference between this method and AnnotatedElement.getDeclaredAnnotation(Class) is that this method detects if its argument is a repeatable annotation type (JLS 9.6), and if so, attempts to find one or more annotations of that type by "looking through" a container annotation if one is present. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
      Specified by:
      getDeclaredAnnotationsByType in interface AnnotatedElement
      Type Parameters:
      A - the type of the annotation to query for and return if directly or indirectly present
      Parameters:
      annotationClass - the Class object corresponding to the annotation type
      Returns:
      all this element's annotations for the specified annotation type if directly or indirectly present on this element, else an array of length zero
      Throws:
      NullPointerException - if the given annotation class is null
      Since:
      1.8

    • getDeclaredAnnotations

      public Annotation[] getDeclaredAnnotations()
      Description copied from interface: AnnotatedElement
      Returns annotations that are directly present on this element. This method ignores inherited annotations. If there are no annotations directly present on this element, the return value is an array of length 0. The caller of this method is free to modify the returned array; it will have no effect on the arrays returned to other callers.
      Specified by:
      getDeclaredAnnotations in interface AnnotatedElement
      Returns:
      annotations directly present on this element
      Since:
      1.5

    • getAnnotatedSuperclass

      public AnnotatedType getAnnotatedSuperclass()
      Returns an AnnotatedType object that represents the use of a type to specify the superclass of the entity represented by this Class object. (The use of type Foo to specify the superclass in '... extends Foo' is distinct from the declaration of type Foo.)

      If this Class object represents a type whose declaration does not explicitly indicate an annotated superclass, then the return value is an AnnotatedType object representing an element with no annotations.

      If this Class represents either the Object class, an interface type, an array type, a primitive type, or void, the return value is null.

      Returns:
      an object representing the superclass
      Since:
      1.8

    • getAnnotatedInterfaces

      public AnnotatedType[] getAnnotatedInterfaces()
      Returns an array of AnnotatedType objects that represent the use of types to specify superinterfaces of the entity represented by this Class object. (The use of type Foo to specify a superinterface in '... implements Foo' is distinct from the declaration of type Foo.)

      If this Class object represents a class, the return value is an array containing objects representing the uses of interface types to specify interfaces implemented by the class. The order of the objects in the array corresponds to the order of the interface types used in the 'implements' clause of the declaration of this Class object.

      If this Class object represents an interface, the return value is an array containing objects representing the uses of interface types to specify interfaces directly extended by the interface. The order of the objects in the array corresponds to the order of the interface types used in the 'extends' clause of the declaration of this Class object.

      If this Class object represents a class or interface whose declaration does not explicitly indicate any annotated superinterfaces, the return value is an array of length 0.

      If this Class object represents either the Object class, an array type, a primitive type, or void, the return value is an array of length 0.

      Returns:
      an array representing the superinterfaces
      Since:
      1.8

    • getNestHost

      public Class<?> getNestHost()
      Returns the nest host of the nest to which the class or interface represented by this Class object belongs. Every class and interface is a member of exactly one nest. A class or interface that is not recorded as belonging to a nest belongs to the nest consisting only of itself, and is the nest host.

      Each of the Class objects representing array types, primitive types, and void returns this to indicate that the represented entity belongs to the nest consisting only of itself, and is the nest host.

      If there is a linkage error accessing the nest host, or if this class or interface is not enumerated as a member of the nest by the nest host, then it is considered to belong to its own nest and this is returned as the host.

      API Note:
      A class file of version 55.0 or greater may record the host of the nest to which it belongs by using the NestHost attribute (JVMS 4.7.28). Alternatively, a class file of version 55.0 or greater may act as a nest host by enumerating the nest's other members with the NestMembers attribute (JVMS 4.7.29). A class file of version 54.0 or lower does not use these attributes.
      Returns:
      the nest host of this class or interface
      Throws:
      SecurityException - If the returned class is not the current class, and if a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for the returned class and invocation of s.checkPackageAccess() denies access to the package of the returned class
      See Java Virtual Machine Specification:
      4.7.28 The NestHost Attribute
      4.7.29 The NestMembers Attribute
      5.4.4 Access Control
      Since:
      11

    • isNestmateOf

      public boolean isNestmateOf​(Class<?> c)
      Determines if the given Class is a nestmate of the class or interface represented by this Class object. Two classes or interfaces are nestmates if they have the same nest host.
      Parameters:
      c - the class to check
      Returns:
      true if this class and c are members of the same nest; and false otherwise.
      Since:
      11

    • getNestMembers

      public Class<?>[] getNestMembers()
      Returns an array containing Class objects representing all the classes and interfaces that are members of the nest to which the class or interface represented by this Class object belongs. The nest host of that nest is the zeroth element of the array. Subsequent elements represent any classes or interfaces that are recorded by the nest host as being members of the nest; the order of such elements is unspecified. Duplicates are permitted. If the nest host of that nest does not enumerate any members, then the array has a single element containing this.

      Each of the Class objects representing array types, primitive types, and void returns an array containing only this.

      This method validates that, for each class or interface which is recorded as a member of the nest by the nest host, that class or interface records itself as a member of that same nest. Any exceptions that occur during this validation are rethrown by this method.

      Returns:
      an array of all classes and interfaces in the same nest as this class
      Throws:
      LinkageError - If there is any problem loading or validating a nest member or its nest host
      SecurityException - If any returned class is not the current class, and if a security manager, s, is present and the caller's class loader is not the same as or an ancestor of the class loader for that returned class and invocation of s.checkPackageAccess() denies access to the package of that returned class
      Since:
      11
      See Also:
      getNestHost()

    • descriptorString

      public String descriptorString()
      Returns the type descriptor string for this class.

      Note that this is not a strict inverse of forName(java.lang.String); distinct classes which share a common name but have different class loaders will have identical descriptor strings.

      Specified by:
      descriptorString in interface TypeDescriptor
      Returns:
      the type descriptor representation
      See Java Virtual Machine Specification:
      4.3.2 Field Descriptors
      Since:
      12

    • componentType

      public Class<?> componentType()
      Returns the component type of this Class, if it describes an array type, or null otherwise.
      Specified by:
      componentType in interface TypeDescriptor.OfField<T>
      Implementation Requirements:
      Equivalent to getComponentType().
      Returns:
      a Class describing the component type, or null if this Class does not describe an array type
      Since:
      12

    • arrayType

      public Class<?> arrayType()
      Returns a Class for an array type whose component type is described by this Class.
      Specified by:
      arrayType in interface TypeDescriptor.OfField<T>
      Returns:
      a Class describing the array type
      Since:
      12

    • describeConstable

      public Optional<ClassDesc> describeConstable()
      Returns a nominal descriptor for this instance, if one can be constructed, or an empty Optional if one cannot be.
      Specified by:
      describeConstable in interface Constable
      Returns:
      An Optional containing the resulting nominal descriptor, or an empty Optional if one cannot be constructed.
      Since:
      12