Java之遍历Map

public class mapTest {

    public static void main(String[] args) {
        Map<Integer, Integer> map = new HashMap<Integer, Integer>(); 
        map.put(1, 1);
        map.put(2, 2);
        map.put(3, 3);
        add1(map);
        add2(map);
        add3(map);
        add4(map);
    }
    
    //循环map
    public static Map<String,Object> add1(Map<Integer, Integer> map) {
        for (Map.Entry<Integer, Integer> entry : map.entrySet()) { 
          System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); 
        }
        return null;
    }
    
    //key  value 单独取
    public static Map<String,Object> add2(Map<Integer, Integer> map) {
        for (Integer key : map.keySet()) { 
              System.out.println("Key = " + key); 
            } 
            //遍历map中的值 
            for (Integer value : map.values()) { 
              System.out.println("Value = " + value); 
            }
        return null;
    }
    
    //使用Iterator遍历
    public static Map<String,Object> add3(Map<Integer, Integer> map) {
        Iterator<Map.Entry<Integer, Integer>> entries = map.entrySet().iterator(); 
        while (entries.hasNext()) { 
          Map.Entry<Integer, Integer> entry = entries.next(); 
          System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue()); 
        }
        return null;
    }

    public static Map<String,Object> add4(Map<Integer, Integer> map) {
        for (Integer key : map.keySet()) { 
              Integer value = map.get(key); 
              System.out.println("Key = " + key + ", Value = " + value);
        }
        return null;
    }
}

PS:如果仅需要键(keys)或值(values)使用方法二。如果你使用的语言版本低于java 5，或是打算在遍历时删除entries，必须使用方法三。否则使用方法一(键值都要)。

转自:https://www.cnblogs.com/fqfanqi/p/6187085.html