Chapter 11
The java.io Package

FilterWriter

Name

FilterWriter

Synopsis

Class Name:

java.io.FilterWriter

Superclass:

java.io.Writer

Immediate Subclasses:

None

Interfaces Implemented:

None

Availability:

New as of JDK 1.1

The FilterWriter class is the superclass of all of the writer classes that filter output. A subclass of FilterWriter works by wrapping an existing writer, called the underlying writer, and providing additional functionality. The methods of FilterWriter simply override the methods of Writer with versions that call the corresponding methods of the underlying writer.

FilterWriter cannot be instantiated directly; it must be subclassed. An instance of a subclass of FilterWriter is constructed with another Writer object. The methods of a subclass of FilterWriter should override some methods in order to extend their behavior or provide some sort of filtering.

FilterWriter is like FilterOutputStream, except that it deals with a character stream instead of a byte stream.

Class Summary

public abstract class java.io.FilterWriter extends java.io.Writer {
  // Variables
  protected Writer out;
  // Constructors
  protected FilterWriter(Writer out);
  // Instance Methods
  public void close();
  public void flush();
  public void write(int c);
  public void write(char[] cbuf, int off, int len);
  public void write(String str, int off, int len);
}

Variables

out

protected Writer out

Description: The underlying writer that this FilterWriter wraps or filters.

Constructors

FilterWriter

public FilterWriter(Writer out)

Parameters

out: The output writer to filter.

Description

This constructor creates a FilterWriter that sends data to out.

Instance Methods

close

public void close() throws IOException

Throws

IOException: If any kind of I/O error occurs.

Overrides

Writer.close()

Description

This method calls the close() method of the underlying writer, which releases any system resources associated with this object.

flush

public void flush() throws IOException

Throws

IOException: If any kind of I/O error occurs.

Overrides

Writer.flush()

Description

This method calls the flush() method of the underlying writer, which forces any characters that may be buffered by this FilterWriter to be written to the underlying device.

write

public void write(int c) throws IOException

Parameters

c: The value to write.

Throws

IOException: If any kind of I/O error occurs.

Overrides

Writer.write(int)

Description

This method writes a character containing the low-order 16 bits of the given integer value. It calls the write(int) method of the underlying writer.

 public void write(char[] cbuf, int off, int len) throws IOException

Parameters

cbuf

An array of characters to write to the stream.

off

An offset into the array.

len

The number of characters to write.

Throws

IOException: If any kind of I/O error occurs.

Overrides

Writer.write(char[], int, int)

Description

This method writes len characters contained in the given array, starting at offset off. It does this by calling the write(char[], int, int) method of the underlying writer.

public void write(String str, int off, int len) throws IOException

Parameters

str

A string to write to the stream.

off

An offset into the string.

len

The number of characters to write.

Throws

IOException: If any kind of I/O error occurs.

Overrides

Writer.write(String, int, int)

Description

This method writes len characters contained in the given string, starting at offset off. It does this by calling the write(String, int, int) method of the underlying writer.

Inherited Methods

Method	Inherited From	Method	Inherited From
`clone()`	`Object`	`equals(Object)`	`Object`
`finalize()`	`Object`	`getClass()`	`Object`
`hashCode()`	`Object`	`notify()`	`Object`
`notifyAll()`	`Object`	`toString()`	`Object`
`wait()`	`Object`	`wait(long)`	`Object`
`wait(long, int)`	`Object`