java - Java中的单例设计模式和单例对象有什么区别？

Question

这是最近在采访中被问到的问题。根据我的说法，通过单例模式我们可以实例化单例对象。但是，我想知道我是否正确。

Answer 1

你是对的，单例设计模式用于实例化单例对象:

SingleObject class provides a static method to get its static instance to outside world. SingletonPatternDemo, our demo class will use SingleObject class to get a SingleObject object. source

代码看起来像这样:

public class SingleObject {

    //create an object of SingleObject
    private static SingleObject instance = new SingleObject();

    //make the constructor private so that this class cannot be
    //instantiated
    private SingleObject() {
    }

    //Get the only object available
    public static SingleObject getInstance() {
        return instance;
    }

    public void showMessage() {
        System.out.println("Hello World!");
    }
}

要调用 SingleObject 类:

public class SingletonPatternDemo {

    public static void main(String[] args) {
        //illegal construct
        //Compile Time Error: The constructor SingleObject() is not visible
        //SingleObject object = new SingleObject();

        //Get the only object available
        SingleObject object = SingleObject.getInstance();

        //show the message
        object.showMessage();
    }
}

因此，单例设计模式描述了如何使用单例对象。 WikiLink

请记住，单例实际上是伪装的全局变量。 因此 Singletons 被认为已被弃用。