import java.util.ArrayList;import java.util.HashMap;import java.util.Iterator;import java.util.List;import java.util.Map;import java.util.Set;public class zengzhiwei {    public static void main(String agrs[]) {        System.out.println("hello world!");        Map
     
       m = new HashMap
      
       ();        m.put("zengzhiwei", "zzw");        m.put("zengzhijie", "zzj");            Set
       
         s = m.keySet();        Iterator
        
          itr = s.iterator();        while(itr.hasNext()) {            Object o = itr.next();            System.out.println(m.get(o));        }                List
         
           l = new ArrayList
          
           (); l.add(1); l.add(2); l.add(3); System.out.println(l.toString()); for (int i = 0; i < l.size(); i++) { System.out.println(l.get(i)); } }}
          
         
        
       
      
     

hello world!zzwzzj[1, 2, 3]123