Module java.compiler
Package javax.lang.model.type

Interface TypeVisitor<R,​P>

  • Type Parameters:
    R - the return type of this visitor's methods. Use Void for visitors that do not need to return results.
    P - the type of the additional parameter to this visitor's methods. Use Void for visitors that do not need an additional parameter.
    All Known Implementing Classes:
    AbstractTypeVisitor6, AbstractTypeVisitor7, AbstractTypeVisitor8, AbstractTypeVisitor9, SimpleTypeVisitor6, SimpleTypeVisitor7, SimpleTypeVisitor8, SimpleTypeVisitor9, TypeKindVisitor6, TypeKindVisitor7, TypeKindVisitor8, TypeKindVisitor9
    public interface TypeVisitor<R,​P>
    A visitor of types, in the style of the visitor design pattern. Classes implementing this interface are used to operate on a type when the kind of type is unknown at compile time. When a visitor is passed to a type's accept method, the visitXyz method most applicable to that type is invoked.

    Classes implementing this interface may or may not throw a NullPointerException if the additional parameter p is null; see documentation of the implementing class for details.

    WARNING: It is possible that methods will be added to this interface to accommodate new, currently unknown, language structures added to future versions of the Java™ programming language. Therefore, visitor classes directly implementing this interface may be source incompatible with future versions of the platform. To avoid this source incompatibility, visitor implementations are encouraged to instead extend the appropriate abstract visitor class that implements this interface. However, an API should generally use this visitor interface as the type for parameters, return type, etc. rather than one of the abstract classes.

    Note that methods to accommodate new language constructs could be added in a source compatible way if they were added as default methods. However, default methods are only available on Java SE 8 and higher releases and the javax.lang.model.* packages bundled in Java SE 8 were required to also be runnable on Java SE 7. Therefore, default methods were not used when extending javax.lang.model.* to cover Java SE 8 language features. However, default methods are used in subsequent revisions of the javax.lang.model.* packages that are only required to run on Java SE 8 and higher platform versions.

    Since:
    1.6

    • Method Detail

      • visit

        R visit​(TypeMirror t,
        P p)
        Visits a type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visit

        default R visit​(TypeMirror t)
        A convenience method equivalent to visit(t, null).
        Implementation Requirements:
        The default implementation is visit(t, null).
        Parameters:
        t - the element to visit
        Returns:
        a visitor-specified result

      • visitPrimitive

        R visitPrimitive​(PrimitiveType t,
                 P p)
        Visits a primitive type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitNull

        R visitNull​(NullType t,
            P p)
        Visits the null type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitArray

        R visitArray​(ArrayType t,
             P p)
        Visits an array type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitDeclared

        R visitDeclared​(DeclaredType t,
                P p)
        Visits a declared type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitError

        R visitError​(ErrorType t,
             P p)
        Visits an error type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitTypeVariable

        R visitTypeVariable​(TypeVariable t,
                    P p)
        Visits a type variable.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitWildcard

        R visitWildcard​(WildcardType t,
                P p)
        Visits a wildcard type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitExecutable

        R visitExecutable​(ExecutableType t,
                  P p)
        Visits an executable type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitNoType

        R visitNoType​(NoType t,
              P p)
        Visits a NoType instance.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result

      • visitUnknown

        R visitUnknown​(TypeMirror t,
               P p)
        Visits an unknown kind of type. This can occur if the language evolves and new kinds of types are added to the TypeMirror hierarchy.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result
        Throws:
        UnknownTypeException - a visitor implementation may optionally throw this exception

      • visitUnion

        R visitUnion​(UnionType t,
             P p)
        Visits a union type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result
        Since:
        1.7

      • visitIntersection

        R visitIntersection​(IntersectionType t,
                    P p)
        Visits an intersection type.
        Parameters:
        t - the type to visit
        p - a visitor-specified parameter
        Returns:
        a visitor-specified result
        Since:
        1.8