How to List Java System Properties

package com.darwinsys;
 
/*
 * Copyright (c) Ian F. Darwin, http://www.darwinsys.com/, 1996-2002. All rights reserved. Software
 * written by Ian F. Darwin and others. $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
 * 
 * Redistribution and use in source and binary forms, with or without modification, are permitted
 * provided that the following conditions are met: 1. Redistributions of source code must retain the
 * above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions
 * in binary form must reproduce the above copyright notice, this list of conditions and the
 * following disclaimer in the documentation and/or other materials provided with the distribution.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND ANY EXPRESS OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS;
 * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
 * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * Java, the Duke mascot, and all variants of Sun's Java "steaming coffee cup" logo are trademarks
 * of Sun Microsystems. Sun's, and James Gosling's, pioneering role in inventing and promulgating
 * (and standardizing) the Java language and environment is gratefully acknowledged.
 * 
 * The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for inventing predecessor
 * languages C and C++ is also gratefully acknowledged.
 */
 
import java.io.IOException;
 
/**
 * List one or more item(s) from System Properties
 */
public class SysPropDemo {
    public static void main(String[] argv) throws IOException {
	if (argv.length == 0)
	    System.getProperties().store(System.out, "System Properties:");
	else
	    for (int i = 0; i < argv.length; i++) {
		String s = argv[i];
		System.out.println(s + " = " + System.getProperties().getProperty(s));
	    }
    }
}