Writer implementation which provides a means for writing directly to a JTextArea

import java.io.Writer;
import java.io.IOException;

import javax.swing.JTextArea;

/** A implementation of the java.io.Writer class which facilitates writing to a JTextArea via a stream.

<p><b>Note:</b> There appears to be bug in the Macintosh implementation of
the JDK 1.1 where a PrintWriter writing to this class will not include the
correct line feeds for display in a JTextArea. There is a simple test of
the "java.version" system property which, if it starts with the String "1.1"
will cause newlines to be written each time the buffer is flushed.</p>

@author Anthony Eden
*/

public class JTextAreaWriter extends Writer{

private boolean closed = false;
private JTextArea textArea;
private StringBuffer buffer;

/** Constructor.

@param textArea The JTextArea to write to.
*/

public JTextAreaWriter(JTextArea textArea){
setTextArea(textArea);
}

/** Set the JTextArea to write to.

@param textArea The JTextArea
*/

public void setTextArea(JTextArea textArea){
if(textArea == null){
throw new IllegalArgumentException("The text area must not be null.");
}
this.textArea = textArea;
}

/** Close the stream. */

public void close(){
closed = true;
}

/** Flush the data that is currently in the buffer.

@throws IOException
*/

public void flush() throws IOException{
if(closed){
throw new IOException("The stream is not open.");
}
// the newline character should not be necessary. The PrintWriter
// should autmatically put the newline, but it doesn't seem to work
textArea.append(getBuffer().toString());
if(System.getProperty("java.version").startsWith("1.1")){
textArea.append("\n");
}
textArea.setCaretPosition(textArea.getDocument().getLength());
buffer = null;
}

/** Write the given character array to the output stream.

@param charArray The character array
@throws IOException
*/

public void write(char[] charArray) throws IOException{
write(charArray, 0, charArray.length);
}

/** Write the given character array to the output stream beginning from
the given offset and proceeding to until the given length is reached.

@param charArray The character array
@param offset The start offset
@param length The length to write
@throws IOException
*/

public void write(char[] charArray, int offset, int length) throws IOException{
if(closed){
throw new IOException("The stream is not open.");
}
getBuffer().append(charArray, offset, length);
}

/** Write the given character to the output stream.

@param c The character
@throws IOException
*/

public void write(int c) throws IOException{
if(closed){
throw new IOException("The stream is not open.");
}
getBuffer().append((char)c);
}

/** Write the given String to the output stream.

@param string The String
@throws IOException
*/

public void write(String string) throws IOException{
if(closed){
throw new IOException("The stream is not open.");
}
getBuffer().append(string);
}

/** Write the given String to the output stream beginning from the given offset
and proceeding to until the given length is reached.

@param string The String
@param offset The start offset
@param length The length to write
@throws IOException
*/

public void write(String string, int offset, int length) throws IOException{
if(closed){
throw new IOException("The stream is not open.");
}
getBuffer().append(string.substring(offset, length));
}

// protected methods

/** Get the StringBuffer which holds the data prior to writing via
a call to the <code>flush()

method. This method should
never return null.

@return A StringBuffer
*/

protected StringBuffer getBuffer(){
if(buffer == null){
buffer = new StringBuffer();
}
return buffer;
}

}