~~~ public class Person { private Person(){ System.out.println("对象初始化"); } public static class SingletonClassInstance{ private static final Person person = new Person(); } public static Person getInstance(){ System.out.println("get instance"); return SingletonClassInstance.person; } } ~~~ ``` 优点 1. 使用时才初始化 2. 安全性（不被反射入侵） 缺点 1. ```