[Java] HashMap走訪器

HashMap hm = new HashMap();
hm.put("a", 1);
hm.put("b", 2);
hm.put("c", 3);
Set set = new HashSet();
set =  hm.keySet();
Iterator it = set.iterator();

String s;
while (it.hasNext()) {
    s = it.next().toString();
    System.out.println( s + " = " + hm.get(s).toString());
}