用于Java Void参考类型？ [英] Uses for the Java Void Reference Type?

问题描述

有一个Java Void - 大写V-- 引用类型。我见过的唯一情况是参数化可调用 s

There is a Java Void -- uppercase V-- reference type. The only situation I have ever seen it used is to parameterize Callables

final Callable<Void> callable = new Callable<Void>() {
            public Void call() {
                foobar();
                return null;
            }
        };

Java Void还有其他用途参考类型？是否可以分配 null 以外的任何内容？如果是的话，你有例子吗？

Are there any other uses for the Java Void reference type? Can it ever be assigned anything other than null? If yes, do you have examples?

推荐答案

Void 已成为惯例对于您不感兴趣的泛型参数。没有理由要使用任何其他非实例化类型，例如 System 。

Void has become convention for a generic argument that you are not interested in. There is no reason why you should use any other non-instantiable type, such as System.

它也常用于例如 Map 值（尽管 Collections.newSetFromMap 使用 Boolean 因为地图不必接受 null values）和 java.security.PrivilegedAction 。

It is also often used in for example Map values (although Collections.newSetFromMap uses Boolean as maps don't have to accept null values) and java.security.PrivilegedAction.

我写了 Void 的noreferrer>博客条目。

I wrote a weblog entry on Void a few years back.

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