package testUtility;import java.util.HashMap;import java.util.Iterator;import java.util.Set;import java.util.Vector;import java.util.Map.Entry;public class test_condense{public static void main(String[] args) {HashMap<Integer,Integer> map = new HashMap<Integer,Integer>();HashMap<Integer,Vector<Integer>> revert = new HashMap<Integer,Vector<Integer>>();map.put(4, 2);map.put(5, 2);map.put(1, 6);map.put(3, 6);map.put(7, 1);Set<Entry<Integer, Integer>> set = map.entrySet();Iterator<Entry<Integer, Integer>> itor = set.iterator();while(itor.hasNext()){Entry<Integer, Integer> entry = itor.next();int NumberwithOccurance = entry.getKey();int Occurance = entry.getValue();if( revert.containsKey(entry.getValue()) == false){Vector<Integer> NumberListWithSameOccurance = new Vector<Integer>();NumberListWithSameOccurance.add(NumberwithOccurance);revert.put(Occurance, NumberListWithSameOccurance);}else{Vector<Integer> existingNumberList = revert.get(Occurance);existingNumberList.add(NumberwithOccurance);revert.put(Occurance, existingNumberList);}}Set<Entry<Integer, Vector<Integer>>> Revertset = revert.entrySet();Iterator<Entry<Integer, Vector<Integer>>> Revertitor = Revertset.iterator();while(Revertitor.hasNext()){Entry<Integer, Vector<Integer>> entry = Revertitor.next();System.out.println("Occruance: " + entry.getKey());for( int i = 0 ; i < entry.getValue().size(); i ++){System.out.println("Number with same Occurance: " + entry.getValue().elementAt(i));}}}}这是测试数据：key为双色球号码，value为该号码出现次数，比如(4,2)意思就是4号球出现了两次。

　　执行代码，输出：

　　Occruance: 1Number with same Occurance: 7Occruance: 2Number with same Occurance: 4Number with same Occurance: 5Occruance: 6Number with same Occurance: 1Number with same Occurance: 3意思是7号球出现了一次，4号球和5号球出现了2次，依次类推。