单例模式（懒汉）（一）

/**
 * 单例模式（懒汉）线程不安全
 */

public class Single {

    private static Single single=null;

    private Single(){

    }

    public static Single getInstance(){
        if (single == null){
            single=new Single();
        }
        return single;
    }

测试是否为单例

public static void main(String[] args) {
        Single single1 = Single.getInstance();
        Single single2 = Single.getInstance();
        System.out.println(single1 == single2);
 }