Java API中的单例类示例 [英] Examples of singleton classes in the Java APIs

问题描述

Java API中Singleton设计模式的最佳示例是什么？ Runtime 类是单例吗？

What are the best examples of the Singleton design pattern in the Java APIs? Is the Runtime class a singleton?

推荐答案

只有两个例子注意：

• java.lang.Runtime＃getRuntime（）


• java.awt.Desktop＃getDesktop（）

• java.lang.Runtime#getRuntime()
• java.awt.Desktop#getDesktop()

请参见也：

• Java API中GoF设计模式的真实示例

• Real world examples of GoF Design Patterns in Java API

更新：要回答PeterMmm（当前已删除？）的评论（问我如何知道这是一个单例），请检查javadoc和源代码：

Update: to answer PeterMmm's (currently deleted?) comment (which asked how I knew that it was a singleton), check the javadoc and source code:

public class Runtime {
    private static Runtime currentRuntime = new Runtime();

    /**
     * Returns the runtime object associated with the current Java application.
     * Most of the methods of class <code>Runtime</code> are instance 
     * methods and must be invoked with respect to the current runtime object. 
     * 
     * @return  the <code>Runtime</code> object associated with the current
     *          Java application.
     */
    public static Runtime getRuntime() { 
        return currentRuntime;
    }

    /** Don't let anyone else instantiate this class */
    private Runtime() {}

每次都返回相同的实例，并且具有 private 构造函数。

It returns the same instance everytime and it has a private constructor.

这篇关于Java API中的单例类示例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！