TestSingleton.java

public class TestSingleton {

    public static void main(String[] args) {
        Singleton singleton = Singleton.getInstance();
        singleton.name = "张三";
        Singleton singleton1 = Singleton.getInstance();
        System.out.println(singleton1.name);
    }

}

class Singleton {

    public String name;

    private static Singleton singleton;

    public static Singleton getInstance() {
        if (singleton == null)
            singleton = new Singleton();
        return singleton;
    }

}