Java 不能实例化地图...为什么不呢？
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Can't Instantiate Map...well why not?
提问by PinkElephantsOnParade
Map<String, ArrayList<Pair<String, Integer>>> k = new Map<String, ArrayList<Pair<String, Integer>>>();
This line is in my code. I'd like to instantiate a Map that contains a String then an ArrayList of Pairs of Strings and Integers.
这一行在我的代码中。我想实例化一个 Map，它包含一个字符串，然后是一个字符串和整数对的 ArrayList。
Pair is a class that I wrote that is in my package.
Pair 是我在包中编写的一个类。
I get "Cannot Instantiate the type Map>>();
我得到“无法实例化类型 Map>>();
Why not? Seems reasonable to me...
为什么不？对我来说似乎很合理...
采纳答案by rgettman
The built-in Mapis an interface, which cannot be instantiated. You can choose between lots of implementing concrete classes on the right side of your assignment, such as:
内置Map是一个接口，不能实例化。您可以在作业右侧的许多实现具体类之间进行选择，例如：
ConcurrentHashMapHashMapLinkedHashMapTreeMap
ConcurrentHashMapHashMapLinkedHashMapTreeMap
and many others. The Javadocs for Maplists many direct concrete implementations.
和许多其他人。该Javadoc文档Map列出了许多直接的具体实现。
回答by Hussain Akhtar Wahid 'Ghouri'
Interfaces cant be intantiated You need to use some concrete class implementing the interface Try something like this
接口不能被初始化你需要使用一些实现接口的具体类试试这样的
Map<String, ArrayList<Pair<String, Integer>>> k = new HashMap<String, ArrayList<Pair<String, Integer>>>();
