设计模式单例模式

来源：互联网发布：python 创建临时文件编辑：程序博客网时间：2024/06/07 20:27

懒汉式单例

public class Singleton {  private static Singleton uniqueInstance;  private Singleton(){};  public static Singleton getInstance() {    if (uniqueInstance==null) {        uniqueInstance=new Singleton();    }       return uniqueInstance;}  public static void main(String[] args) {    Singleton singleton=Singleton.getInstance();    Singleton singleton1=Singleton.getInstance();    System.out.println(singleton==singleton1);}}

2.这种模式在多线程下是不安全的，可以加synchronized关键字

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

双重机制

public static Singleton getInstance() {          if (singleton == null) {                synchronized (Singleton.class) {                   if (singleton == null) {                      singleton = new Singleton();                  }                }            }            return singleton;       }

3.饿汉式单例，天生就线程安全，有final关键字

public class Singleton1 {    private Singleton1() {}      private static final Singleton1 single = new Singleton1();      //静态工厂方法       public static Singleton1 getInstance() {          return single;      }      public static void main(String[] args) {    Singleton1 sin=Singleton1.getInstance();    Singleton1 sin1=Singleton1.getInstance();    System.out.println(sin==sin1);    }}

参考自http://blog.csdn.net/jason0539/article/details/23297037/

阅读全文

0 0