2018-10-26 看懂单例

//懒汉式单例
public class SingleTwo {
    private SingleTwo() {
    }

    private static SingleTwo singleTwo = null;

    public static SingleTwo getSingleTwo() {
        if (singleTwo == null) {
            singleTwo = new SingleTwo();
        }
        return singleTwo;
    }

}
//饿汉式单例
public class Single {
    private Single() {
    }
    private static Single single = new Single();
    public static Single getSingle(){
        return  single;
    }


    public static void main(String[] args) {
        //单例与非单例的区别
        StringBuffer stringBuffer = new StringBuffer();
        StringBuffer stringBuffer1 = new StringBuffer();
        System.out.println(stringBuffer.equals(stringBuffer1));//false
        Single single = Single.getSingle();
        Single single1 = Single.getSingle();
        System.out.println(single.equals(single1));//true
        SingleTwo singleTwo = SingleTwo.getSingleTwo();
        SingleTwo singleTwo1 = SingleTwo.getSingleTwo();
        System.out.println(singleTwo.equals(singleTwo1));//true
        //单例可以保证我们总是在操作同一个对象
    }
}