1 package singleInstance; 2 /**饿汉式，类加载时候创建实例，浪费资源，线程是安全的*/ 3 public class SingleDome01 { 4     //私有构造方法，防止直接new对象 5     private SingleDome01() { 6     } 7     //类加载的时候，创建对象 8     private static SingleDome01 instance = new SingleDome01(); 9     //提供getter，方便外界访问私有对象10     11     public static SingleDome01 getInstance() {12         return instance;13     }14 }

 1 package singleInstance; 2 /**懒汉式，被调用时候才会实例化，节约资源，高并发线程时不安全*/ 3 public class SingleDome02 { 4     //私有构造方法，防止直接new对象 5     private SingleDome02(){ 6     } 7     private static SingleDome02 instance; 8     //提供getter,以便外界调用私有对象，返回SingleDome02对象 9     public static SingleDome02 getInstance() {10         if(instance==null){11             instance = new SingleDome02();12         }13         return instance;14     }15 }