Map循环的三种方法

 import java.util.HashMap;
 import java.util.Iterator;
 import java.util.Map;

 public class MapTest {
     public static void main(String[] args){

         Map<String,String> map = new HashMap<String,String>();
         map.put("1", "a");
         map.put("2", "b");
         map.put("3", "c");

         //通过Map.keySet()遍历key和value,二次取值
         for(String key:map.keySet()){
             System.out.println(key + map.get(key));
         }

         //通过Map.entrySet()遍历key和value(推荐使用)
         for(Map.Entry<String, String> entry:map.entrySet()){
             System.out.println(entry.getKey() + entry.getValue());
         }

         //通过Map.entrySet()使用iterator()遍历key和value
         Iterator<Map.Entry<String, String>> iterator = map.entrySet().iterator();
         while(iterator.hasNext()){
             Map.Entry<String, String> entry = iterator.next();
             System.out.println(entry.getKey() + entry.getValue());
         }
     }
 }