import java.util.Properties;
import java.util.Enumeration;
...
// Get a list of all the system properties and their values
// Not available in unsigned Applets, only applications and signed Applets.
Properties sysprops = System .getProperties();
for ( Enumeration e = sysprops.propertyNames(); e.hasMoreElements(); )
   {
   String key = (String)e.nextElement();
   String value = sysprops.getProperty( key );
   out.println( key + "=" + value );
   } // end for