Map的精髓---------遍历Map集合

 1.通过迭代器遍历

public class Testmap {
    public static void main(String[] args) throws Exception{
      Map<Integer,String> map=new HashMap<>();
      map.put(1,"hello");
      map.put(2,"hello");
      map.put(3,"baby");
        //1.将map转换为set集合
        Set<Map.Entry<Integer,String>> set=map.entrySet();
        //2.获取iterator对象
        Iterator<Map.Entry<Integer,String>> iterator=set.iterator();
        while(iterator.hasNext()){
           Map.Entry<Integer,String> entry=iterator.next();
            System.out.println(entry.getKey()+":"+entry.getValue());
        }
    }
}

2.基于迭代器,以foreach遍历

public class Testmap {
    public static void main(String[] args) throws Exception {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "hello");
        map.put(2, "hello");
        map.put(3, "baby");
        System.out.println(map); 
         for (Map.Entry<Integer, String> entry : map.entrySet()) {
            System.out.println(entry.getKey());
            System.out.println(entry.getValue());
           }
       }
}

3.通过遍历key遍历Map

public class Testmap {
    public static void main(String[] args) throws Exception {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "hello");
        map.put(2, "hello");
        map.put(3, "baby");
        System.out.println(map);
        for (Integer key : map.keySet()) {
            String value = map.get(key);
        }
          }
}
 

 4.通过Value遍历

public class Testmap {
    public static void main(String[] args) throws Exception {
        Map<Integer, String> map = new HashMap<>();
        map.put(1, "hello");
        map.put(2, "hello");
        map.put(3, "baby");
        System.out.println(map);
      for (String value : map.values()){
          System.out.println(value);
          }
       }
}