有趣的Java泛型

问题描述

任何人都知道如何使用泛型编写下面的代码片段，并避免编译器警告？ （@SuppressWarnings（unchecked）被认为是作弊）。

也许，通过泛型来检查left的类型与

pre $ public void assertLessOrEqual（Comparable left，Comparable right）{
if（left == null || right == null ||（left.compareTo（right）> 0））{
String msg =[+ left +]不小于[+ right +];
抛出新的RuntimeException（assertLessOrEqual：+ msg）;


$ / code>




解决方案

可与Comparable类型的子类一起工作：



  public< T extends Comparable< super T>> void assertLessOrEqual（T left，T right）{
 if（left == null || right == null || left.compareTo（right）> 0）{
 String msg =[+左+]不小于[+右+]; 
抛出新的RuntimeException（assertLessOrEqual：+ msg）; 
} 
} 
  




Anybody knows how to write the piece of code below using generics AND avoiding compiler warnings ? (@SuppressWarnings("unchecked") is considered cheating).

And, maybe, checking via generics that the type of "left" is the same as the type of "right" ?

public void assertLessOrEqual(Comparable left, Comparable right) {
    if (left == null || right == null || (left.compareTo(right) > 0)) {
        String msg = "["+left+"] is not less than ["+right+"]";
        throw new RuntimeException("assertLessOrEqual: " + msg);
    }
}

解决方案

This works with subclasses of Comparable types too:

public <T extends Comparable<? super T>> void assertLessOrEqual(T left, T right) {
  if (left == null || right == null || left.compareTo(right) > 0) {
    String msg = "["+left+"] is not less than ["+right+"]";
    throw new RuntimeException("assertLessOrEqual: " + msg);
  }
}

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