discarding output : Java Glossary

discarding output

Sometimes the user does not want the output of a Java program. How can you, as programmer, efficiently discard it without having to insert ifs around every write? You need a NullOutputStream class, an implementation of OutputStream that does nothing with the output given to it.

// 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 JavaDoc Subversion repository.

This technique is more efficient than writing to the “NUL” device, since no bytes are sent to the OS, 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" )));

Thanks go to John B. Matthews for the information.

file i/o

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