根据键名从 HashMap 获取字符串值 [英] get string value from HashMap depending on key name

问题描述

我有一个带有各种键和值的 HashMap，我怎样才能得到一个值?

I have a HashMap with various keys and values, how can I get one value out?

我在地图中有一个名为 my_code 的键，它应该包含一个字符串，我怎样才能在不必遍历地图的情况下获得它?

I have a key in the map called my_code, it should contain a string, how can I just get that without having to iterate through the map?

到目前为止我有..

   HashMap newMap = new HashMap(paramMap);
   String s = newMap.get("my_code").toString();

我期待看到一个 String，例如ABC"或DEF"，因为这是我最初放入的内容，但如果我执行 System.out.println() 我得到类似 java.lang.string#F0454

I'm expecting to see a String, such as "ABC" or "DEF" as that is what I put in there initially, but if I do a System.out.println() I get something like java.lang.string#F0454

抱歉，我对地图不太熟悉，你可能猜到了;)

Sorry, I'm not too familiar with maps as you can probably guess ;)

推荐答案

只需使用 Map#get(key) ?

Just use Map#get(key) ?

Object value = map.get(myCode);

这里有一个关于地图的教程，你可能会发现它很有用:http://java.sun.com/docs/books/tutorial/collections/interfaces/map.html.

Here's a tutorial about maps, you may find it useful: http://java.sun.com/docs/books/tutorial/collections/interfaces/map.html.

您使用以下内容编辑了您的问题:

you edited your question with the following:

我期待看到一个字符串，例如ABC"或DEF"，因为这是我最初放入的内容，但是如果我执行 System.out.println() 我得到类似java.lang.string#F0454

抱歉，我对地图不太熟悉，你可能猜到了;)

您正在看到 Object#toString().但是 java.lang.String 应该已经实现了，除非您创建了一个 custom 实现，名称中带有小写的 s:java.lang.string.如果它实际上是一个自定义对象，那么无论何时执行 System.out.println() 都需要重写 Object#toString() 以获得人类可读的字符串"> 或 toString() 在所需的对象上.例如:

You're seeing the outcome of Object#toString(). But the java.lang.String should already have one implemented, unless you created a custom implementation with a lowercase s in the name: java.lang.string. If it is actually a custom object, then you need to override Object#toString() to get a "human readable string" whenever you do a System.out.println() or toString() on the desired object. For example:

@Override
public String toString() {
    return "This is Object X with a property value " + value;
}

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