饿汉单例模式示例

 1 public class SingleInstance {
 2     /*
 3         饿汉单例模式：在用类创建对象的时候，对象就已经准备好了
 4             1.定义一个类，把构造器私有
 5             2.定义一个静态变量存储一个对象
 6      */
 7     public static SingleInstance instance = new SingleInstance();
 8     private SingleInstance(){}
 9 
10     public static void main(String[] args) {
11         SingleInstance instance1 = SingleInstance.instance;
12         SingleInstance instance2 = SingleInstance.instance;
13         SingleInstance instance3 = SingleInstance.instance;
14 
15         System.out.println(instance1);
16         System.out.println(instance2);
17         System.out.println(instance3);
18         System.out.println(instance1 == instance3);
19     }
20 }