泛型和Java中的排序 [英] Generics and sorting in Java

问题描述

假设你在Java中编写一个静态函数来对数组进行排序，就像 Arrays.sort（）一样。 Arrays.sort（）的问题在于它接收一个Object数组，如果元素的元素抛出 ClassCastException 不要实现 Comparable 。

所以你希望你的函数接收一个子类型数组作为参数可比。类似的东西可以工作：

  static< T extends Comparable> void sort（T [] array）; 
  

该签名的问题在于，您仍然可以传递一个可比较数组与整数和字符串，这会导致 RuntimeException 。

所以，你如何创建一个函数，元素实现Comparable并且具有所有相同的类型（例如Integer，String等）？

解决方案

使用

  static< T extends Comparable< ;? super T>> sort（T [] array）; 
  

这是完成任务最常规的规范。基本上，它断言， T 是一种可以与自身进行比较的类型。

Suppose you write a static function in Java to sort an array, much like Arrays.sort(). The problem with Arrays.sort() is that it receives an array of Object, and throws a ClassCastException if its elements don't implement Comparable.

So you want your function to receive as an argument an array of a subtype of Comparable. Something like that could work:

static <T extends Comparable> void sort(T[] array);

The problem with that signature is that you can still pass an array of Comparables with Integers and Strings for instance, which would cause a RuntimeException.

So, how can you create a function that will receive only an array whose elements implement Comparable and have all the same type (e.g. Integer, String, etc?)

解决方案

Use

static <T extends Comparable<? super T>> sort(T[] array);

which is the most general specification to accomplish the task. Basically, it asserts, that T is a type which can be compared to itself.

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