Java 创建键值对象列表
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Create a list of key value objects
提问by john cs
I am trying to create a list of key-value pairs. Here is what I have so far:
我正在尝试创建一个键值对列表。这是我到目前为止所拥有的：
Map<Integer,String> map = new HashMap<Integer,String>().put(songID, songList.get(i).name);
This gives me the following error:
这给了我以下错误：
Type mismatch: cannot convert from String to Map
类型不匹配：无法从 String 转换为 Map
Also, how would I iterate through these? Thanks!
另外，我将如何遍历这些？谢谢！
采纳答案by Juned Ahsan
When you call puton the map of type Map <Integer,String>, you will get the String returned. So when you do this:
当您调用puttype 的地图时Map <Integer,String>，您将获得返回的字符串。所以当你这样做时：
new HashMap<Integer,String>().put(songID, songList.get(i).name);
it will return a String
它会返回一个 String
and when you try to assign it to a map
当您尝试将其分配给地图时
Map<Integer,String> map
compiler throws an error,
编译器抛出错误，
Type mismatch: cannot convert from String to Map
类型不匹配：无法从 String 转换为 Map
Here is the signature of put method form javadocs:
这是javadocs中 put 方法的签名：
public V put(K key,
V value)
you need to break down the this complex problematic statement:
你需要分解这个复杂的有问题的陈述：
Map<Integer,String> map = new HashMap<Integer,String>().put(songID, songList.get(i).name);
to something like:
类似于：
Map<Integer,String> map = new HashMap<Integer,String>();
map.put(songID, songList.get(i).name);
回答by Daniel Gabriel
The answer on this thread: Java HashMap associative multi dimensional array can not create or add elements
此线程的答案： Java HashMap 关联多维数组无法创建或添加元素
has an example of how to do this.
有一个如何做到这一点的例子。
