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Singleton2.java
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32 lines (27 loc) · 1.08 KB
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package singleton;
import java.util.Date;
/**
* Created by helmeter on 5/3/16.
*/
public class Singleton2 {
//volatile提醒编译器它后面所定义的变量随时都有可能改变，因此编译后的程序每次需要存储或读取这个变量的时候，
// 都会直接从变量地址中读取数据。如果没有volatile关键字，则编译器可能优化读取和存储，可能暂时使用寄存器中的值，
// 如果这个变量由别的程序更新了的话，将出现不一致的现象
private volatile static Singleton2 uniqueInstance;
private Date date = null ; // 对象创建的时间
private Singleton2(){date = new Date();}
public static Singleton2 getInstance(){
if(uniqueInstance == null){
synchronized (Singleton2.class){
if(uniqueInstance == null){
uniqueInstance = new Singleton2();
}
}
}
return uniqueInstance;
}
// do something
public void doSomething(){
System.out.println("Create at "+date.toString());
}
}