Java 6 Map.get（）类型安全意外行为（？） [英] Java 6 Map.get() Type Safety Unexpected Behavior(?)

问题描述

可能存在重复：

为什么Map.get（对象键）不是（完全）通用的原因

根据javadocs（ http://java.sun.com/javase/6/docs/api/java/util/Map.html ）对于Map接口，get的定义是

V get（Object key）
返回指定键映射到的值，或者如果此映射包含null
没有为
键的映射。

代码示例：

  Map< InstrumentInfo，Double> moo = new HashMap< InstrumentInfo，Double>（）; 
 moo.get（new Integer（5））; 
  

我期望上面的代码会抛出异常或者至少发出警告。

我认为在泛型和类型安全性方面，get方法会带入一个类型参数。在这个问题中讨论

stackoverflow.com/questions/857420/what-are-the-reasons-why-map-getobject-key-is-not-fully-generic\">为什么Map.get（Object key）不是（完全）通用的，以及...

Possible Duplicate:
What are the reasons why Map.get(Object key) is not (fully) generic

According to the javadocs (http://java.sun.com/javase/6/docs/api/java/util/Map.html) for the Map interface, the definition of get is

V get(Object key) Returns the value to which the specified key is mapped, or null if this map contains no mapping for the key.

Code Example:

Map<InstrumentInfo, Double> moo = new HashMap<InstrumentInfo,Double>();
moo.get(new Integer(5));

I would expect that the above code will throw an exception or at least give a warning.

I would expect that with generics and type safety, the get method would take in a parameter of type . What is the reason for taking in type Object and not ?

解决方案

Discussed in this question What are the reasons why Map.get(Object key) is not (fully) generic, as well...

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