标签：class 单例设计 ret out 饿汉 单例设计模式 err code sys
一,单例设计模式懒汉式和恶汉式
懒汉式在类加载时不初始化，延迟加载。（配置文件）
饿汉式在类加载时初始化，加载慢，获取对象快。
饿汉式是线程安全的，
懒汉式需要加synchronized，否则不安全。
二，饿汉式
1 public class Singletonehan { 2 private static Singletonehan singleton=new Singletonehan(); 3 private Singletonehan() { 4 } 5 public static Singletonehan getInstance(){ 6 return singleton; 7 } 8 9 @Override 10 public String toString() { 11 return "Singletonehan{}"; 12 } 13 }
测试
1 public class testehan { 2 public static void main(String[] args) { 3 Singletonehan singletonehan = Singletonehan.getInstance(); 4 System.out.println(singletonehan); 5 } 6 }
三，懒汉式
1 public class Singletonlanhan { 2 // private static Singletonlanhan singleton=new Singletonlanhan(); 3 private static Singletonlanhan singleton=null; 4 5 private Singletonlanhan() { 6 } 7 8 public static Singletonlanhan getInstance() { 9 if (singleton == null) { 10 singleton = new Singletonlanhan(); 11 } 12 return singleton; 13 } 14 15 @Override 16 public String toString() { 17 return "Singletonlanhan{}"; 18 } 19 }
测试
1 public class test { 2 public static void main(String[] args) { 3 Singletonlanhan singletonlanhan = Singletonlanhan.getInstance(); 4 System.out.println(singletonlanhan); 5 } 6 }
结果
Singletonlanhan{}
Process finished with exit code 0
补充加synchronized后的懒汉
1 public class Singletonlanhan { 2 // private static Singletonlanhan singleton=new Singletonlanhan(); 3 private static Singletonlanhan singleton=null; 4 5 private Singletonlanhan() { 6 } 7 8 public synchronized static Singletonlanhan getInstance() { 9 if (singleton == null) { 10 singleton = new Singletonlanhan(); 11 } 12 return singleton; 13 } 14 15 @Override 16 public String toString() { 17 return "锁Singletonlanhan{}"; 18 } 19 }
结果
锁Singletonlanhan{}
Process finished with exit code 0
标签：class 单例设计 ret out 饿汉 单例设计模式 err code sys
原文地址：https://www.cnblogs.com/fengtangjiang/p/11106102.html
