Module java.base
Package java.io

Class Writer

java.lang.Object
java.io.Writer
All Implemented Interfaces:
Closeable, Flushable, Appendable, AutoCloseable
Direct Known Subclasses:
BufferedWriter, CharArrayWriter, FilterWriter, OutputStreamWriter, PipedWriter, PrintWriter, StringWriter

public abstract class Writer
extends Object
implements Appendable, Closeable, Flushable
Abstract class for writing to character streams. The only methods that a subclass must implement are write(char[], int, int), flush(), and close(). Most subclasses, however, will override some of the methods defined here in order to provide higher efficiency, additional functionality, or both.
Since:
1.1
See Also:
BufferedWriter, CharArrayWriter, FilterWriter, OutputStreamWriter, FileWriter, PipedWriter, PrintWriter, StringWriter, Reader
  • Field Summary

    Fields
    Modifier and Type Field Description
    protected Object lock
    The object used to synchronize operations on this stream.
  • Constructor Summary

    Constructors
    Modifier Constructor Description
    protected Writer()
    Creates a new character-stream writer whose critical sections will synchronize on the writer itself.
    protected Writer​(Object lock)
    Creates a new character-stream writer whose critical sections will synchronize on the given object.
  • Method Summary

    Modifier and Type Method Description
    Writer append​(char c)
    Appends the specified character to this writer.
    Writer append​(CharSequence csq)
    Appends the specified character sequence to this writer.
    Writer append​(CharSequence csq, int start, int end)
    Appends a subsequence of the specified character sequence to this writer.
    abstract void close()
    Closes the stream, flushing it first.
    abstract void flush()
    Flushes the stream.
    static Writer nullWriter()
    Returns a new Writer which discards all characters.
    void write​(char[] cbuf)
    Writes an array of characters.
    abstract void write​(char[] cbuf, int off, int len)
    Writes a portion of an array of characters.
    void write​(int c)
    Writes a single character.
    void write​(String str)
    Writes a string.
    void write​(String str, int off, int len)
    Writes a portion of a string.

    Methods declared in class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
  • Field Details

    • lock

      protected Object lock
      The object used to synchronize operations on this stream. For efficiency, a character-stream object may use an object other than itself to protect critical sections. A subclass should therefore use the object in this field rather than this or a synchronized method.
  • Constructor Details

    • Writer

      protected Writer()
      Creates a new character-stream writer whose critical sections will synchronize on the writer itself.
    • Writer

      protected Writer​(Object lock)
      Creates a new character-stream writer whose critical sections will synchronize on the given object.
      Parameters:
      lock - Object to synchronize on
  • Method Details

    • nullWriter

      public static Writer nullWriter()
      Returns a new Writer which discards all characters. The returned stream is initially open. The stream is closed by calling the close() method. Subsequent calls to close() have no effect.

      While the stream is open, the append(char), append(CharSequence), append(CharSequence, int, int), flush(), write(int), write(char[]), and write(char[], int, int) methods do nothing. After the stream has been closed, these methods all throw IOException.

      The object used to synchronize operations on the returned Writer is not specified.

      Returns:
      a Writer which discards all characters
      Since:
      11
    • write

      public void write​(int c) throws IOException
      Writes a single character. The character to be written is contained in the 16 low-order bits of the given integer value; the 16 high-order bits are ignored.

      Subclasses that intend to support efficient single-character output should override this method.

      Parameters:
      c - int specifying a character to be written
      Throws:
      IOException - If an I/O error occurs
    • write

      public void write​(char[] cbuf) throws IOException
      Writes an array of characters.
      Parameters:
      cbuf - Array of characters to be written
      Throws:
      IOException - If an I/O error occurs
    • write

      public abstract void write​(char[] cbuf, int off, int len) throws IOException
      Writes a portion of an array of characters.
      Parameters:
      cbuf - Array of characters
      off - Offset from which to start writing characters
      len - Number of characters to write
      Throws:
      IndexOutOfBoundsException - Implementations should throw this exception if off is negative, or len is negative, or off + len is negative or greater than the length of the given array
      IOException - If an I/O error occurs
    • write

      public void write​(String str) throws IOException
      Writes a string.
      Parameters:
      str - String to be written
      Throws:
      IOException - If an I/O error occurs
    • write

      public void write​(String str, int off, int len) throws IOException
      Writes a portion of a string.
      Implementation Requirements:
      The implementation in this class throws an IndexOutOfBoundsException for the indicated conditions; overriding methods may choose to do otherwise.
      Parameters:
      str - A String
      off - Offset from which to start writing characters
      len - Number of characters to write
      Throws:
      IndexOutOfBoundsException - Implementations should throw this exception if off is negative, or len is negative, or off + len is negative or greater than the length of the given string
      IOException - If an I/O error occurs
    • append

      public Writer append​(CharSequence csq) throws IOException
      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
      Parameters:
      csq - The character sequence to append. If csq is null, then the four characters "null" are appended to this writer.
      Returns:
      This writer
      Throws:
      IOException - If an I/O error occurs
      Since:
      1.5
    • append

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

      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
      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()
      IOException - If an I/O error occurs
      Since:
      1.5
    • append

      public Writer append​(char c) throws IOException
      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
      Parameters:
      c - The 16-bit character to append
      Returns:
      This writer
      Throws:
      IOException - If an I/O error occurs
      Since:
      1.5
    • flush

      public abstract void flush() throws IOException
      Flushes the stream. If the stream has saved any characters from the various write() methods in a buffer, write them immediately to their intended destination. Then, if that destination is another character or byte stream, flush it. Thus one flush() invocation will flush all the buffers in a chain of Writers and OutputStreams.

      If the intended destination of this stream is an abstraction provided by the underlying operating system, for example a file, then flushing the stream guarantees only that bytes previously written to the stream are passed to the operating system for writing; it does not guarantee that they are actually written to a physical device such as a disk drive.

      Specified by:
      flush in interface Flushable
      Throws:
      IOException - If an I/O error occurs
    • close

      public abstract void close() throws IOException
      Closes the stream, flushing it first. Once the stream has been closed, further write() or flush() invocations will cause an IOException to be thrown. Closing a previously closed stream has no effect.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException - If an I/O error occurs