[Java] Java中的Map允许有重复元素吗?

package com.test.collection;
import java.util.hashmap;
import java.util.map;
//map中key值不可重复的测试
public class testequals {
  public static void main(string[] args) {
  string s1=new string("abc");
  string s2=new string("abc");
  map map=new hashmap();
  map.put(s1, "abc123");
  map.put(s2, "abc456");//第二个会覆盖第一个元素
  //注意：map中key值不可重复，直接根据比较的是equals,只有equals相同则覆盖
  system.out.println(map.size());
  system.out.println(map.get(s1));
  }
}

1
abc456

public class test {
  public static map putsome(map<string,string> map){
  map.put("gender", "male");
  map.put("name", "athor");
  map.put("name", "cindy");
  map.put("name", "billy");
  map.put("from","china");
  return map;
  }
  public static void main(string[] args) {
  system.out.println(putsome(new hashmap<string,string>()));
  system.out.println(putsome(new treemap<string,string>()));
  system.out.println(putsome(new linkedhashmap<string,string>()));
  }
}

{name=billy, gender=male, from=china}
{from=china, gender=male, name=billy}
{gender=male, name=billy, from=china}