Java泛型？ [英] Java Generics?

问题描述

多年来，我看到许多人使用泛型这个词，我真的不知道它的意思，不管它是我最有可能使用它，但不知道它被称为那个。 ：p

解决方案

From http://java.sun.com/j2se/1.5.0/docs/guide/language/generics.html

泛型为您提供了一种将集合的类型传递给编译器的方法，以便可以对其进行检查。一旦编译器知道集合的元素类型，编译器就可以检查你是否一直使用集合，并且可以在集合中取出的值上插入正确的强制转换。

<这是一个从现有集合教程中取得的简单示例：

  //删除4来自c的字母单词。 （Iterator i = c.iterator（）; i.hasNext（）;）
 if（（（String）i。 next（））。length（）== 4）
 i.remove（）; 
 
 
 code 
 
 
lockquote 
 
这里是相同的例子修改为使用泛型：
 
 
 
 
  //从c $ b $中移除4个字母的单词（Iterator< String> i = c.iterator（）; i.hasNext（）;）
 if（i.next（）。length （）== 4）
 i.remove（）; 
 
} 
  
对不起，我发现这个写出来比我能写的要好。
 
 
 
编辑包括评论中的一个优点：$ b​​ 
 $ b < blockquote> 
 
 泛型不限于
将集合
的类型传递给编译器......集合
库恰好是一个好东西
来展示它们。 
 
 
 
Over the years I seen many people use the word "generics", I honestly have not a clue what it means, whatever it is I most likely use it but just don't know that it was called that. :p
解决方案
From http://java.sun.com/j2se/1.5.0/docs/guide/language/generics.html

  
Generics provides a way for you to communicate the type of a collection to the compiler, so that it can be checked. Once the compiler knows the element type of the collection, the compiler can check that you have used the collection consistently and can insert the correct casts on values being taken out of the collection.
  
  
Here is a simple example taken from the existing Collections tutorial:


    // Removes 4-letter words from c. Elements must be strings
    static void expurgate(Collection c) {
        for (Iterator i = c.iterator(); i.hasNext(); )
          if (((String) i.next()).length() == 4)
            i.remove();

}



  
Here is the same example modified to use generics:


    // Removes the 4-letter words from c
    static void expurgate(Collection<String> c) {
        for (Iterator<String> i = c.iterator(); i.hasNext(); )
          if (i.next().length() == 4)
            i.remove();

}
Sorry for the direct c&p but I found that this write up was better than something I could have written.

Edit to include a good point made in the comments: 

  
Generics are not limited to
  communicating the type of a collection
  to the compiler...the collections
  library just happened to be a good way
  to demonstrate them.


                        
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