JavaMap

 1 import java.util.*;
 2 
 3 public class AddingGroups {
 4 
 5     public static void main(String[] args) {
 6         
 7         Random rnd = new Random(10);
 8         Map<Integer,Integer> m = new HashMap<Integer,Integer>();
 9         for(int i=0;i<10000;i++)
10         {
11             int r = rnd.nextInt(10);
12             Integer cnt = m.get(r);
13             m.put(r, cnt == null ? 1:cnt+1);
14         }
15         Set<Integer> keySet = (Set<Integer>) m.keySet();
16         List<Integer> valueList = new ArrayList<Integer>();
17         for(Integer i:keySet)
18         {
19             valueList.add(m.get(i));
20         }
21         
22         //通过产生迭代器的遍历
23         Iterator<Integer> it =  m.keySet().iterator();
24         while( it.hasNext() )
25         {
26             System.out.print(it.next());
27         }
28         System.out.println();
29         System.out.println(m);
30         System.out.println(keySet);
31         System.out.println(valueList);
32         
33     }
34 }