JavaMap

import java.util.*;

public class AddingGroups {

    public static void main(String[] args) {
        
        Random rnd = new Random(10);
        Map<Integer,Integer> m = new HashMap<Integer,Integer>();
        for(int i=0;i<10000;i++)
        {
            int r = rnd.nextInt(10);
            Integer cnt = m.get(r);
            m.put(r, cnt == null ? 1:cnt+1);
        }
        Set<Integer> keySet = (Set<Integer>) m.keySet();
        List<Integer> valueList = new ArrayList<Integer>();
        for(Integer i:keySet)
        {
            valueList.add(m.get(i));
        }
        
        //通过产生迭代器的遍历
        Iterator<Integer> it =  m.keySet().iterator();
        while( it.hasNext() )
        {
            System.out.print(it.next());
        }
        System.out.println();
        System.out.println(m);
        System.out.println(keySet);
        System.out.println(valueList);
        
    }
}