Look at the documentation: PrintWriter (Java Platform SE 7 )
It says very clearly:
Unlike the PrintStream class, if automatic flushing is enabled it will be done only when one of the println, printf, or format methods is invoked, rather than whenever a newline character happens to be output. These methods use the platform's own notion of line separator rather than the newline character.
So if you don't use println, nothing will happen to the output.