Map.Entry: getKey()
import java.util.Iterator; import java.util.Map; import java.util.Properties; public class Main { public static void main(String[] a) { Properties props = System.getProperties(); Iterator iter = props.entrySet().iterator(); while (iter.hasNext()) { Map.Entry entry = (Map.Entry) iter.next(); System.out.println(entry.getKey() + " -- " + entry.getValue()); } } }