单例模式
http://baike.baidu.com/view/1859857.htm
单例模式一般有三种形式
//1.饿汉式
public class Singleton1 {
private static Singleton1 instance = new Singleton1();
private Singleton1() {
}
static Singleton1 getInstance() {
return instance;
}
}
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//2.懒汉式
public class Singleton2 {
private static Singleton2 instance = null;
private Singleton2() {
}
static Singleton2 getInstance() {
if (instance == null)
instance = new Singleton2();
return instance;
}
}
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//双重锁的形式。
public class Singleton3 {
private static Singleton3 instance = null;
private Singleton3(){
//do something
}
public static Singleton3 getInstance(){
if(instance==null){
synchronized(Singleton3.class){
if(null == instance){
instance = new Singleton3();
}
}
}
return instance;
}
}