懒汉工厂测试

package com.aaa.demo;

public class JavaStudy implements ISoftwareStudy{
    @Override
    public void study() {
        System.out.println("JAVA study");
    }
}

package com.aaa.demo;

public class PhthonStudy implements ISoftwareStudy {
    @Override
    public void study() {
        System.out.println("Phonth study");
    }
}

package com.aaa.demo;

public class UIStudy implements ISoftwareStudy {
    @Override
    public void study() {
        System.out.println("UI study");
    }
}

package com.aaa.demo;

public interface ISoftwareStudy {
    void study();
}

package com.aaa.demo;

public class AFactory {
    public ISoftwareStudy getStudy(int num){
        ISoftwareStudy s=null;

        if (num==1){
            s=new JavaStudy();
        }else if(num==2){
            s=new PhthonStudy();
        }else if(num==3){
            s=new UIStudy();
        }
        return s;
        /**
         *
         * */
    }
}

package com.aaa.demo;

/*
* 饿汉单例模式
* */
public class HungryDemo {
    private HungryDemo(){

    }
    //静态的：在内存中只存在一个全局
    private static HungryDemo s= new HungryDemo();
    private static HungryDemo y=new HungryDemo();

    public static HungryDemo getInstance(){
        System.out.println("this change has come into effect!");
        return s;
    }

    public static HungryDemo getInstances(){
        System.out.println("This change has come into effect!");
        return y;
    }
}

package com.aaa.demo;

/*
* 饿汉单例模式
* */
public class HungryDemo {
    private HungryDemo(){

    }
    //静态的：在内存中只存在一个全局
    private static HungryDemo s= new HungryDemo();
    private static HungryDemo y=new HungryDemo();

    public static HungryDemo getInstance(){
        System.out.println("this change has come into effect!");
        return s;
    }

    public static HungryDemo getInstances(){
        System.out.println("This change has come into effect!");
        return y;
    }
}

package com.aaa.demo;

public class StarvingDemp {
    private StarvingDemp(){

    }
    private static StarvingDemp s=null;

    public static StarvingDemp getInstance(){
        if(null==s){
            s=new StarvingDemp();
        }else {
            System.out.println("this ok");
        }
        return s;
    }
}