设计模式之单例工厂模式

1.单例类

public class Singleton {
    private Singleton(){};
    public void doSomething(){
        System.out.println("do some thing");
    }
}

2.单例工厂类

package com.example.demo.entity;
import java.lang.reflect.Constructor;

public class SingletonFactory {
    private static Singleton singleton;
    static {
        try {
            Class cl= Class.forName(Singleton.class.getName());
            //获得无参构造
            Constructor constructor=cl.getDeclaredConstructor();
            //设置无参构造是可访问的
            constructor.setAccessible(true);
            singleton =(Singleton) constructor.newInstance();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    public static Singleton getSingleton(){
        return singleton;
    }
}

　　3.场景类

package com.example.demo.entity;

public class Client {
    public static void main(String[] args) {
        Singleton singleton = SingletonFactory.getSingleton();
        singleton.doSomething();
    }
}