图解设计模式Singleton模式

只生成一个实例的模式被称作单例模式

UML

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Singleton

public class Singleton {
    private static Singleton singleton = new Singleton();

    private Singleton() {
        System.out.println("生成了一个实例");
    }

    public static Singleton getInstance() {
        return singleton;
    }
}

Main

public class Main {

    public static void main(String[] args) {
    // write your code here
        System.out.println("Start.");
        Singleton obj1 = Singleton.getInstance();
        Singleton obj2 = Singleton.getInstance();
        if (obj1 == obj2) {
            System.out.println("obj1 与 obj2是相同的实例.");
        } else {
            System.out.println("obj1 与 obj2是不同的实例");
        }
        System.out.println("End.");
    }
}