Java泛型？

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();

}

对不起直接c& p,但我发现这个写作比我写的更好.

编辑以在评论中包含一个好点：

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.