hashMap 中 key和value交换

import java.util.HashMap;
import java.util.Hashtable;
import java.util.Set;
import java.util.Collection;

class TestCollection{
	public static void main(String[] args) {
     
     HashMap<String,String> hashMap = new HashMap<String,String>();
     hashMap.put("aaa","111");    
      hashMap.put("bbb","222");    
      hashMap.put("ccc","333");    
      int i=0;
      System.out.println(hashMap);
      HashMap<String,String> hashMap2 = new HashMap<String,String>();
     int size=hashMap.size();
     String [] key=new String[size]; 
     String [] val=new String[size];
     for(String a:hashMap.keySet()){//keySet 取出hashMap中的所有key
     	val[i]=a;
     	key[i]=hashMap.get(a);
     	i++;

	}

	for(int a=0;a<size;a++){
		hashMap2.put(key[a],val[a]);
	}
	System.out.println(hashMap2);
    }
}