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
The base class for all writers. A writer is a means of writing data to a target in a character-wise manner. Most output streams expect the flush() method to be called before closing the stream, to ensure all data is actually written out.

This abstract class does not provide a fully working implementation, so it needs to be subclassed, and at least the write(char[], int, int), close() and flush() methods needs to be overridden. Overriding some of the non-abstract methods is also often advised, since it might result in higher efficiency.

Many specialized readers for purposes like reading from a file already exist in this package.

See Also:
Reader

  • Field Summary

    Fields
    Modifier and Type Field Description
    protected Object lock
    The object used to synchronize access to the writer.

  • Constructor Summary

    Constructors
    Modifier Constructor Description
    protected Writer()
    Constructs a new Writer with this as the object used to synchronize critical sections.
    protected Writer​(Object lock)
    Constructs a new Writer with lock used to synchronize critical sections.

  • Method Summary

    Modifier and Type Method Description
    Writer append​(char c)
    Appends the character c to the target.
    Writer append​(CharSequence csq)
    Appends the character sequence csq to the target.
    Writer append​(CharSequence csq, int start, int end)
    Appends a subsequence of the character sequence csq to the target.
    abstract void close()
    Closes this writer.
    abstract void flush()
    Flushes this writer.
    void write​(char[] buf)
    Writes the entire character buffer buf to the target.
    abstract void write​(char[] buf, int offset, int count)
    Writes count characters starting at offset in buf to the target.
    void write​(int oneChar)
    Writes one character to the target.
    void write​(String str)
    Writes the characters from the specified string to the target.
    void write​(String str, int offset, int count)
    Writes count characters from str starting at offset to the target.

    Methods inherited from 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 access to the writer.

  • Constructor Details

    • Writer

      protected Writer()
      Constructs a new Writer with this as the object used to synchronize critical sections.

    • Writer

      protected Writer​(Object lock)
      Constructs a new Writer with lock used to synchronize critical sections.
      Parameters:
      lock - the Object used to synchronize critical sections.
      Throws:
      NullPointerException - if lock is null.

  • Method Details

    • close

      public abstract void close() throws IOException
      Closes this writer. Implementations of this method should free any resources associated with the writer.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Throws:
      IOException - if an error occurs while closing this writer.

    • flush

      public abstract void flush() throws IOException
      Flushes this writer. Implementations of this method should ensure that all buffered characters are written to the target.
      Specified by:
      flush in interface Flushable
      Throws:
      IOException - if an error occurs while flushing this writer.

    • write

      public void write​(char[] buf) throws IOException
      Writes the entire character buffer buf to the target.
      Parameters:
      buf - the non-null array containing characters to write.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.

    • write

      public abstract void write​(char[] buf, int offset, int count) throws IOException
      Writes count characters starting at offset in buf to the target.
      Parameters:
      buf - the non-null character array to write.
      offset - the index of the first character in buf to write.
      count - the maximum number of characters to write.
      Throws:
      IndexOutOfBoundsException - if offset < 0 or count < 0, or if offset + count is greater than the size of buf.
      IOException - if this writer is closed or another I/O error occurs.

    • write

      public void write​(int oneChar) throws IOException
      Writes one character to the target. Only the two least significant bytes of the integer oneChar are written.
      Parameters:
      oneChar - the character to write to the target.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.

    • write

      public void write​(String str) throws IOException
      Writes the characters from the specified string to the target.
      Parameters:
      str - the non-null string containing the characters to write.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.

    • write

      public void write​(String str, int offset, int count) throws IOException
      Writes count characters from str starting at offset to the target.
      Parameters:
      str - the non-null string containing the characters to write.
      offset - the index of the first character in str to write.
      count - the number of characters from str to write.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.
      IndexOutOfBoundsException - if offset < 0 or count < 0, or if offset + count is greater than the length of str.

    • append

      public Writer append​(char c) throws IOException
      Appends the character c to the target. This method works the same way as write(int).
      Specified by:
      append in interface Appendable
      Parameters:
      c - the character to append to the target stream.
      Returns:
      this writer.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.

    • append

      public Writer append​(CharSequence csq) throws IOException
      Appends the character sequence csq to the target. This method works the same way as Writer.write(csq.toString()). If csq is null, then the string "null" is written to the target stream.
      Specified by:
      append in interface Appendable
      Parameters:
      csq - the character sequence appended to the target.
      Returns:
      this writer.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.

    • append

      public Writer append​(CharSequence csq, int start, int end) throws IOException
      Appends a subsequence of the character sequence csq to the target. This method works the same way as Writer.writer(csq.subsequence(start, end).toString()). If csq is null, then the specified subsequence of the string "null" will be written to the target.
      Specified by:
      append in interface Appendable
      Parameters:
      csq - the character sequence appended to the target.
      start - the index of the first char in the character sequence appended to the target.
      end - the index of the character following the last character of the subsequence appended to the target.
      Returns:
      this writer.
      Throws:
      IOException - if this writer is closed or another I/O error occurs.
      IndexOutOfBoundsException - if start > end, start < 0, end < 0 or either start or end are greater or equal than the length of csq.