如何实例化Map.Entry< K，V>数组在Java？ [英] How do you instantiate a Map.Entry<K, V> array in Java?

问题描述

可能重复：

Java泛型：包含泛型的数组

类，它包含从数组中添加和删除元素的两种方法。为了使它通用，它需要一个子类型，所以它应该能够处理不同类型的对象。

问题是，当我实例化使用MapEntry java.util.Map.Entry的实现）作为子类型。这导致在尝试将对象数组转换为MapEntry数组时抛出ClassCastException。我猜这是因为以下行（其中T是子类型）：

  array =（T []） （new Object [array.length + 1]）; 
 array =（T []）（new Object [array.length  -  1]）; 
  

分别用于将数组大小增加/减少1。我也使用这个在整数，字符串和对象的数组，它的工作正常与那些。

此外，它明确表示，我需要使用数组，没有列表等。

有没有办法解决这个问题，同时仍然保持类作为通用的可能？

编辑：管理以解决问题。这里是工作代码：

  array =（T []）Array.newInstance（array.getClass（）。getComponentType array.length + 1）; 
 array =（T []）Array.newInstance（array.getClass（）。getComponentType（），array.length  -  1）;感谢所有的帮助：D 
 
 
 
 
 $ b >解决方案
 A）不使用数组，他们是可怕的。使用集合。
 
 
 
 B）不能在不知道数组类型的情况下创建通用数组。如果你有类型（类），你可以做：
  T [] array = Array.newInstance长度）; 
  
阅读：
 
 
 
 
 
   Array.newInstance（class，length）  
 
 
 
  Java如何：创建通用数组 
 
 
 

  
Possible Duplicate:

  Java Generics: Array containing generics  
I have a Java class which contains 2 methods which add and remove an element from an array. To make it generic it takes a subtype so it should be able to work on different types of objects.

The problem is that when I instantiate it using MapEntry (where MapEntry is an implementation of java.util.Map.Entry) as the subtype. This results in a ClassCastException being thrown when trying to convert an Object array to a MapEntry array. I'm guessing this is because of the following lines (Where T is the subtype):
array = (T[])(new Object[array.length + 1]);
array = (T[])(new Object[array.length - 1]);
Which are used to increase/decrease the array size by 1 respectively. I also use this on arrays of Integers, Strings and Objects, and it works fine with those.

Also, it's explicitly stated that I need to use arrays for this, so no lists, etc.

Is there any way to get around this problem while still keeping the class as generic as possible?

Edit: Managed to get the problem solved. Here's the working code:
array = (T[])Array.newInstance(array.getClass().getComponentType(), array.length + 1);
array = (T[])Array.newInstance(array.getClass().getComponentType(), array.length - 1);
Thanks for all the help :D
解决方案
A) don't use arrays, they are awful. Use collections instead.

B) you can't create a generic array without knowing the array type. if you do have the type (the class), you can do:
T[] array = Array.newInstance(type, length);
Read:


Array.newInstance(class, length)

Java how to: Generic Array creation


                        
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