Java Map the key variable objects with what consequences?

Conclusion: After put key change in get to get to the null

 

Scala code

    val map = new mutable.HashMap[java.util.List[String], String]()
    val key = new util.ArrayList[String]()
    map.put(key, "value")
    println(map)
    println(map.get(key).getOrElse("null"))
    key.add("11")
    println(map.get(key).getOrElse("null"))
    key.add("111")
    println(map.get(key).getOrElse("null"))

    println(map)