import java.util.HashMap; import java.util.Iterator; import java.util.Set; public class HashSetTest {   public static void main(String[] args) {     HashMap map = new HashMap();     map.put("a", "aa");     map.put("b", "bb");     map.put("c", "cc");     map.put("d", "dd");     map.put("e", "ee");     Set set = map.keySet();     for(Iterator itr=set.iterator();itr.hasNext();){       String value =(String) itr.next();       String key = (String)map.get(value);       System.out.println(value+"="+key);       }   } }