Map.putAll()用法


import Java.util.HashMap;

public class Map_putAllTest {
public static void main(String[] args){
   //两个map具有不同的key
   HashMap map1=new HashMap(); 
   map1.put("1", "A"); 
   HashMap map2 = new HashMap(); 
   map2.put("2", "B"); 
   map2.put("3", "C"); 
   map1.putAll(map2); 
   System.out.println(map1);
   //两个map具有重复的key
   HashMap map3=new HashMap(); 
   map3.put("1", "A"); 
   HashMap map4 = new HashMap(); 
   map4.put("1", "B"); 
   map4.put("3", "C"); 
   map3.putAll(map4); 
   System.out.println(map3);
}
}

输出结果:
{3=C, 2=B, 1=A}
{3=C, 1=B}

结论
.putAll(Map)意思是合并两个Map,如果有相同的Key时,后面的Map覆盖前面的Key和Value

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转载自blog.csdn.net/weixin_43060102/article/details/83017401