discarding output : Java Glossary

// discard all output to System.out and System.err

PrintStream discard = new PrintStream( new NullOutputStream() );
System.setOut( discard );
System.setErr( discard );

You could knock off the trivial code for NullOutputStream yourself or get it from Apache Commons source.

This technique is more efficient than writing to the NUL device, since no bytes are sent to the OS (Operating System), and there is no buffering overhead.

 // discarding output on windows, note "nul" with one l.
System.setOut( new PrintStream( new File( "nul" )));

// discarding output on Unix, note null with two ls.
System.setOut( new PrintStream( new File( "/dev/null" )));