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 Detail

lock

protected Object lock

The object used to synchronize access to the writer.

Constructor Detail

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 Detail

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.