Module java.base
Package java.io

Class PrintWriter

  • All Implemented Interfaces:
    Closeable, Flushable, Appendable, AutoCloseable
    public class PrintWriter
extends Writer
    Prints formatted representations of objects to a text-output stream. This class implements all of the print methods found in PrintStream. It does not contain methods for writing raw bytes, for which a program should use unencoded byte streams.

    Unlike the PrintStream class, if automatic flushing is enabled it will be done only when one of the println, printf, or format methods is invoked, rather than whenever a newline character happens to be output. These methods use the platform's own notion of line separator rather than the newline character.

    Methods in this class never throw I/O exceptions, although some of its constructors may. The client may inquire as to whether any errors have occurred by invoking checkError().

    This class always replaces malformed and unmappable character sequences with the charset's default replacement string. The CharsetEncoder class should be used when more control over the encoding process is required.

    Since:
    1.1

    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected Writer out
      The underlying character-output stream of this PrintWriter.

    • Constructor Summary

      Constructors 
      Constructor Description
      PrintWriter​(File file)
      Creates a new PrintWriter, without automatic line flushing, with the specified file.
      PrintWriter​(File file, String csn)
      Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
      PrintWriter​(File file, Charset charset)
      Creates a new PrintWriter, without automatic line flushing, with the specified file and charset.
      PrintWriter​(OutputStream out)
      Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
      PrintWriter​(OutputStream out, boolean autoFlush)
      Creates a new PrintWriter from an existing OutputStream.
      PrintWriter​(OutputStream out, boolean autoFlush, Charset charset)
      Creates a new PrintWriter from an existing OutputStream.
      PrintWriter​(Writer out)
      Creates a new PrintWriter, without automatic line flushing.
      PrintWriter​(Writer out, boolean autoFlush)
      Creates a new PrintWriter.
      PrintWriter​(String fileName)
      Creates a new PrintWriter, without automatic line flushing, with the specified file name.
      PrintWriter​(String fileName, String csn)
      Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.
      PrintWriter​(String fileName, Charset charset)
      Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset.

    • Method Summary

      Modifier and Type Method Description
      PrintWriter append​(char c)
      Appends the specified character to this writer.
      PrintWriter append​(CharSequence csq)
      Appends the specified character sequence to this writer.
      PrintWriter append​(CharSequence csq, int start, int end)
      Appends a subsequence of the specified character sequence to this writer.
      boolean checkError()
      Flushes the stream if it's not closed and checks its error state.
      protected void clearError()
      Clears the error state of this stream.
      void close()
      Closes the stream and releases any system resources associated with it.
      void flush()
      Flushes the stream.
      PrintWriter format​(String format, Object... args)
      Writes a formatted string to this writer using the specified format string and arguments.
      PrintWriter format​(Locale l, String format, Object... args)
      Writes a formatted string to this writer using the specified format string and arguments.
      void print​(boolean b)
      Prints a boolean value.
      void print​(char c)
      Prints a character.
      void print​(char[] s)
      Prints an array of characters.
      void print​(double d)
      Prints a double-precision floating-point number.
      void print​(float f)
      Prints a floating-point number.
      void print​(int i)
      Prints an integer.
      void print​(long l)
      Prints a long integer.
      void print​(Object obj)
      Prints an object.
      void print​(String s)
      Prints a string.
      PrintWriter printf​(String format, Object... args)
      A convenience method to write a formatted string to this writer using the specified format string and arguments.
      PrintWriter printf​(Locale l, String format, Object... args)
      A convenience method to write a formatted string to this writer using the specified format string and arguments.
      void println()
      Terminates the current line by writing the line separator string.
      void println​(boolean x)
      Prints a boolean value and then terminates the line.
      void println​(char x)
      Prints a character and then terminates the line.
      void println​(char[] x)
      Prints an array of characters and then terminates the line.
      void println​(double x)
      Prints a double-precision floating-point number and then terminates the line.
      void println​(float x)
      Prints a floating-point number and then terminates the line.
      void println​(int x)
      Prints an integer and then terminates the line.
      void println​(long x)
      Prints a long integer and then terminates the line.
      void println​(Object x)
      Prints an Object and then terminates the line.
      void println​(String x)
      Prints a String and then terminates the line.
      protected void setError()
      Indicates that an error has occurred.
      void write​(char[] buf)
      Writes an array of characters.
      void write​(char[] buf, int off, int len)
      Writes A Portion of an array of characters.
      void write​(int c)
      Writes a single character.
      void write​(String s)
      Writes a string.
      void write​(String s, int off, int len)
      Writes a portion of a string.

    • Field Detail

      • out

        protected Writer out
        The underlying character-output stream of this PrintWriter.
        Since:
        1.2

    • Constructor Detail

      • PrintWriter

        public PrintWriter​(Writer out)
        Creates a new PrintWriter, without automatic line flushing.
        Parameters:
        out - A character-output stream

      • PrintWriter

        public PrintWriter​(Writer out,
                   boolean autoFlush)
        Creates a new PrintWriter.
        Parameters:
        out - A character-output stream
        autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer

      • PrintWriter

        public PrintWriter​(OutputStream out)
        Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.
        Parameters:
        out - An output stream
        See Also:
        OutputStreamWriter(java.io.OutputStream)

      • PrintWriter

        public PrintWriter​(OutputStream out,
                   boolean autoFlush)
        Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the default character encoding.
        Parameters:
        out - An output stream
        autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer
        See Also:
        OutputStreamWriter(java.io.OutputStream)

      • PrintWriter

        public PrintWriter​(OutputStream out,
                   boolean autoFlush,
                   Charset charset)
        Creates a new PrintWriter from an existing OutputStream. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will convert characters into bytes using the specified charset.
        Parameters:
        out - An output stream
        autoFlush - A boolean; if true, the println, printf, or format methods will flush the output buffer
        charset - A charset
        Since:
        10

      • PrintWriter

        public PrintWriter​(String fileName)
            throws FileNotFoundException
        Creates a new PrintWriter, without automatic line flushing, with the specified file name. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the default charset for this instance of the Java virtual machine.
        Parameters:
        fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        Throws:
        FileNotFoundException - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        SecurityException - If a security manager is present and checkWrite(fileName) denies write access to the file
        Since:
        1.5

      • PrintWriter

        public PrintWriter​(String fileName,
                   String csn)
            throws FileNotFoundException,
                   UnsupportedEncodingException
        Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
        Parameters:
        fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        csn - The name of a supported charset
        Throws:
        FileNotFoundException - If the given string does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        SecurityException - If a security manager is present and checkWrite(fileName) denies write access to the file
        UnsupportedEncodingException - If the named charset is not supported
        Since:
        1.5

      • PrintWriter

        public PrintWriter​(String fileName,
                   Charset charset)
            throws IOException
        Creates a new PrintWriter, without automatic line flushing, with the specified file name and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
        Parameters:
        fileName - The name of the file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        charset - A charset
        Throws:
        IOException - if an I/O error occurs while opening or creating the file
        SecurityException - If a security manager is present and checkWrite(fileName) denies write access to the file
        Since:
        10

      • PrintWriter

        public PrintWriter​(File file)
            throws FileNotFoundException
        Creates a new PrintWriter, without automatic line flushing, with the specified file. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the default charset for this instance of the Java virtual machine.
        Parameters:
        file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        Throws:
        FileNotFoundException - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        SecurityException - If a security manager is present and checkWrite(file.getPath()) denies write access to the file
        Since:
        1.5

      • PrintWriter

        public PrintWriter​(File file,
                   String csn)
            throws FileNotFoundException,
                   UnsupportedEncodingException
        Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
        Parameters:
        file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        csn - The name of a supported charset
        Throws:
        FileNotFoundException - If the given file object does not denote an existing, writable regular file and a new regular file of that name cannot be created, or if some other error occurs while opening or creating the file
        SecurityException - If a security manager is present and checkWrite(file.getPath()) denies write access to the file
        UnsupportedEncodingException - If the named charset is not supported
        Since:
        1.5

      • PrintWriter

        public PrintWriter​(File file,
                   Charset charset)
            throws IOException
        Creates a new PrintWriter, without automatic line flushing, with the specified file and charset. This convenience constructor creates the necessary intermediate OutputStreamWriter, which will encode characters using the provided charset.
        Parameters:
        file - The file to use as the destination of this writer. If the file exists then it will be truncated to zero size; otherwise, a new file will be created. The output will be written to the file and is buffered.
        charset - A charset
        Throws:
        IOException - if an I/O error occurs while opening or creating the file
        SecurityException - If a security manager is present and checkWrite(file.getPath()) denies write access to the file
        Since:
        10

    • Method Detail

      • close

        public void close()
        Closes the stream and releases any system resources associated with it. Closing a previously closed stream has no effect.
        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        Specified by:
        close in class Writer
        See Also:
        checkError()

      • checkError

        public boolean checkError()
        Flushes the stream if it's not closed and checks its error state.
        Returns:
        true if the print stream has encountered an error, either on the underlying output stream or during a format conversion.

      • setError

        protected void setError()
        Indicates that an error has occurred.

        This method will cause subsequent invocations of checkError() to return true until clearError() is invoked.

      • clearError

        protected void clearError()
        Clears the error state of this stream.

        This method will cause subsequent invocations of checkError() to return false until another write operation fails and invokes setError().

        Since:
        1.6

      • write

        public void write​(int c)
        Writes a single character.
        Overrides:
        write in class Writer
        Parameters:
        c - int specifying a character to be written.

      • write

        public void write​(char[] buf,
                  int off,
                  int len)
        Writes A Portion of an array of characters.
        Specified by:
        write in class Writer
        Parameters:
        buf - Array of characters
        off - Offset from which to start writing characters
        len - Number of characters to write
        Throws:
        IndexOutOfBoundsException - If the values of the off and len parameters cause the corresponding method of the underlying Writer to throw an IndexOutOfBoundsException

      • write

        public void write​(char[] buf)
        Writes an array of characters. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.
        Overrides:
        write in class Writer
        Parameters:
        buf - Array of characters to be written

      • write

        public void write​(String s,
                  int off,
                  int len)
        Writes a portion of a string.
        Overrides:
        write in class Writer
        Parameters:
        s - A String
        off - Offset from which to start writing characters
        len - Number of characters to write
        Throws:
        IndexOutOfBoundsException - If the values of the off and len parameters cause the corresponding method of the underlying Writer to throw an IndexOutOfBoundsException

      • write

        public void write​(String s)
        Writes a string. This method cannot be inherited from the Writer class because it must suppress I/O exceptions.
        Overrides:
        write in class Writer
        Parameters:
        s - String to be written

      • print

        public void print​(boolean b)
        Prints a boolean value. The string produced by String.valueOf(boolean) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        b - The boolean to be printed

      • print

        public void print​(char c)
        Prints a character. The character is translated into one or more bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        c - The char to be printed

      • print

        public void print​(int i)
        Prints an integer. The string produced by String.valueOf(int) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        i - The int to be printed
        See Also:
        Integer.toString(int)

      • print

        public void print​(long l)
        Prints a long integer. The string produced by String.valueOf(long) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        l - The long to be printed
        See Also:
        Long.toString(long)

      • print

        public void print​(float f)
        Prints a floating-point number. The string produced by String.valueOf(float) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        f - The float to be printed
        See Also:
        Float.toString(float)

      • print

        public void print​(double d)
        Prints a double-precision floating-point number. The string produced by String.valueOf(double) is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        d - The double to be printed
        See Also:
        Double.toString(double)

      • print

        public void print​(char[] s)
        Prints an array of characters. The characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        s - The array of chars to be printed
        Throws:
        NullPointerException - If s is null

      • print

        public void print​(String s)
        Prints a string. If the argument is null then the string "null" is printed. Otherwise, the string's characters are converted into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        s - The String to be printed

      • print

        public void print​(Object obj)
        Prints an object. The string produced by the String.valueOf(Object) method is translated into bytes according to the platform's default character encoding, and these bytes are written in exactly the manner of the write(int) method.
        Parameters:
        obj - The Object to be printed
        See Also:
        Object.toString()

      • println

        public void println()
        Terminates the current line by writing the line separator string. The line separator string is defined by the system property line.separator, and is not necessarily a single newline character ('\n').

      • println

        public void println​(boolean x)
        Prints a boolean value and then terminates the line. This method behaves as though it invokes print(boolean) and then println().
        Parameters:
        x - the boolean value to be printed

      • println

        public void println​(char x)
        Prints a character and then terminates the line. This method behaves as though it invokes print(char) and then println().
        Parameters:
        x - the char value to be printed

      • println

        public void println​(int x)
        Prints an integer and then terminates the line. This method behaves as though it invokes print(int) and then println().
        Parameters:
        x - the int value to be printed

      • println

        public void println​(long x)
        Prints a long integer and then terminates the line. This method behaves as though it invokes print(long) and then println().
        Parameters:
        x - the long value to be printed

      • println

        public void println​(float x)
        Prints a floating-point number and then terminates the line. This method behaves as though it invokes print(float) and then println().
        Parameters:
        x - the float value to be printed

      • println

        public void println​(double x)
        Prints a double-precision floating-point number and then terminates the line. This method behaves as though it invokes print(double) and then println().
        Parameters:
        x - the double value to be printed

      • println

        public void println​(char[] x)
        Prints an array of characters and then terminates the line. This method behaves as though it invokes print(char[]) and then println().
        Parameters:
        x - the array of char values to be printed

      • println

        public void println​(String x)
        Prints a String and then terminates the line. This method behaves as though it invokes print(String) and then println().
        Parameters:
        x - the String value to be printed

      • println

        public void println​(Object x)
        Prints an Object and then terminates the line. This method calls at first String.valueOf(x) to get the printed object's string value, then behaves as though it invokes print(String) and then println().
        Parameters:
        x - The Object to be printed.

      • printf

        public PrintWriter printf​(String format,
                          Object... args)
        A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

        An invocation of this method of the form out.printf(format, args) behaves in exactly the same way as the invocation 

        
     out.format(format, args)

        Parameters:
        format - A format string as described in Format string syntax.
        args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
        Returns:
        This writer
        Throws:
        IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
        NullPointerException - If the format is null
        Since:
        1.5

      • printf

        public PrintWriter printf​(Locale l,
                          String format,
                          Object... args)
        A convenience method to write a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

        An invocation of this method of the form out.printf(l, format, args) behaves in exactly the same way as the invocation 

        
     out.format(l, format, args)

        Parameters:
        l - The locale to apply during formatting. If l is null then no localization is applied.
        format - A format string as described in Format string syntax.
        args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
        Returns:
        This writer
        Throws:
        IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
        NullPointerException - If the format is null
        Since:
        1.5

      • format

        public PrintWriter format​(String format,
                          Object... args)
        Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.

        The locale always used is the one returned by Locale.getDefault(), regardless of any previous invocations of other formatting methods on this object.

        Parameters:
        format - A format string as described in Format string syntax.
        args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
        Returns:
        This writer
        Throws:
        IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the Formatter class specification.
        NullPointerException - If the format is null
        Since:
        1.5

      • format

        public PrintWriter format​(Locale l,
                          String format,
                          Object... args)
        Writes a formatted string to this writer using the specified format string and arguments. If automatic flushing is enabled, calls to this method will flush the output buffer.
        Parameters:
        l - The locale to apply during formatting. If l is null then no localization is applied.
        format - A format string as described in Format string syntax.
        args - Arguments referenced by the format specifiers in the format string. If there are more arguments than format specifiers, the extra arguments are ignored. The number of arguments is variable and may be zero. The maximum number of arguments is limited by the maximum dimension of a Java array as defined by The Java™ Virtual Machine Specification. The behaviour on a null argument depends on the conversion.
        Returns:
        This writer
        Throws:
        IllegalFormatException - If a format string contains an illegal syntax, a format specifier that is incompatible with the given arguments, insufficient arguments given the format string, or other illegal conditions. For specification of all possible formatting errors, see the Details section of the formatter class specification.
        NullPointerException - If the format is null
        Since:
        1.5

      • append

        public PrintWriter append​(CharSequence csq)
        Appends the specified character sequence to this writer.

        An invocation of this method of the form out.append(csq) behaves in exactly the same way as the invocation 

        
     out.write(csq.toString())

        Depending on the specification of toString for the character sequence csq, the entire sequence may not be appended. For instance, invoking the toString method of a character buffer will return a subsequence whose content depends upon the buffer's position and limit.

        Specified by:
        append in interface Appendable
        Overrides:
        append in class Writer
        Parameters:
        csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.
        Returns:
        This writer
        Since:
        1.5

      • append

        public PrintWriter append​(CharSequence csq,
                          int start,
                          int end)
        Appends a subsequence of the specified character sequence to this writer.

        An invocation of this method of the form out.append(csq, start, end) when csq is not null, behaves in exactly the same way as the invocation 

        
     out.write(csq.subSequence(start, end).toString())

        Specified by:
        append in interface Appendable
        Overrides:
        append in class Writer
        Parameters:
        csq - The character sequence from which a subsequence will be appended. If csq is null, then characters will be appended as if csq contained the four characters "null".
        start - The index of the first character in the subsequence
        end - The index of the character following the last character in the subsequence
        Returns:
        This writer
        Throws:
        IndexOutOfBoundsException - If start or end are negative, start is greater than end, or end is greater than csq.length()
        Since:
        1.5

      • append

        public PrintWriter append​(char c)
        Appends the specified character to this writer.

        An invocation of this method of the form out.append(c) behaves in exactly the same way as the invocation 

        
     out.write(c)

        Specified by:
        append in interface Appendable
        Overrides:
        append in class Writer
        Parameters:
        c - The 16-bit character to append
        Returns:
        This writer
        Since:
        1.5