java 中map 如何打印map 结构里面的结果呢？

Question

package com.company;
import java.util.HashMap;
import java.util.Map;

public class Main {

    public static void main(String[] args) {
        Map[] map=new Map[5];
        map[0]=new HashMap();
        map[0].put("1","one");
        map[0].put("2","two");
        map[0].put("3","three");
        System.out.print(map);
    }
}

最后的结果是这样的：

[Ljava.util.Map;@1b6d3586
Process finished with exit code 0

表示没看明白这个结果值，我想看到这个map 存的key value 结构内容，如何？

Answer 1

for (Map.Entry<String, String> entry: map.entrySet()) {
    String key = entry.getKey();
    String value = entry.getValue();
}

Answer 2

1. for循环打出来

   // jdk 8+
   for (Map m : map) {
       if (m != null) {
           m.forEach((key, value) -> {
               System.out.println(key + "=" + value);
           });
       }
   }
   // jdk7
   for (Map m : map) {
       if (m != null) {
           for (Object o : m.entrySet()) {
               Map.Entry entry = (Map.Entry) o;
               System.out.println(entry.getKey() + "=" + entry.getValue());
           }
       }
   }

2. 用JSON库比如Jackson来将Map转换为String再打印出来

   System.out.println(new ObjectMapper().writeValueAsString(map));