Graphical User Interfaces - Java - page 577

private private final final JTextArea textArea ;

private private final final StringBuilder sb = new new StringBuilder ();

public public TextAreaOutputStream ( final final JTextArea textArea ) {

this this . textArea = textArea ;

}

@Override
public

public void void flush (){ }

@Override
public

public void void close (){ }

@Override
public

public void void write ( int int b ) throws throws IOException {

iif ( b == '\r' )
return return ;

iif ( b == '\n' ) {
textArea . append ( sb . toString ());
sb . setLength ( 0 );

}

sb . append (( char char ) b );

}

}

As with Writer , we only really need to override three methods; all the others (e.g., Sys-
tem.out.println() ) ultimately call down to this write(int) method. The class shown
here uses a StringBuffer to build up a line of text and, when a line ending comes along, ap-
pends the line to the JTextArea and resets the StringBuffer . A \r is ignored because on
UNIX a \n alone ends a line and on MS-DOS-based systems a \r\n ends a line.

It's not reprinted here, but there is a JUnit test for this class as well. One of the tests is simil-
ar to the one for TextAreaWriter , and the second uses System.setOut() followed by Sys-
tem.out.println() to ensure that everything works as expected. It does.

Here's a longer example of using this. I have an existing console-based Check-
OpenMailRelay program (derived from the mail sender in Sending Email: For Real ), that I
use to test whether remote servers are willing to accept mail from unknown third parties and