单身人士使用AtomicReference [英] Singleton using AtomicReference
本文介绍了单身人士使用AtomicReference的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
使用AtomicReference正确实现延迟初始化单例吗?如果不是 - 可能出现什么问题?
Is it correct implementation of lazy-initializing singleton using AtomicReference? If no - what are the possible issues?
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.util.concurrent.atomic.AtomicReference;
public class Singleton implements Serializable {
private static final Singleton _instance = new Singleton();
private static AtomicReference<Singleton> instance = new AtomicReference<Singleton>();
private Singleton() {
}
public static Singleton getInstance() {
if (instance.compareAndSet(null, _instance)) {
synchronized (_instance) {
_instance.init();
instance.set(_instance);
}
}
return instance.get();
}
private void init() {
// do initialization
}
private Object readResolve() throws ObjectStreamException {
return getInstance();
}
}
推荐答案
不,这很糟糕:
public static Singleton getInstance() {
// new "singleton" for every method call
Singleton s = new Singleton();
^^^^^^^^^^^^^^
if (instance.compareAndSet(null, s)) {
synchronized (s) {
s.init();
}
}
return instance.get();
}
使用AtomicReference是一个不错的主意,但它不起作用,因为Java没有懒惰的评价。
Using an AtomicReference is a nice idea, but it won't work because Java doesn't have lazy evaluation.
经典的1.5单例方法是:
The classic post 1.5 singleton methods are:
渴望单身人士:
public final class Singleton{
private Singleton(){}
private static final Singleton INSTANCE = new Singleton();
public Singleton getInstance(){return INSTANCE;}
}
Lazy Singleton,内部持有者类:
public final class Singleton{
private Singleton(){}
private static class Holder{
private static final Singleton INSTANCE = new Singleton();
}
public Singleton getInstance(){return Holder.INSTANCE;}
}
Enum Singleton:
public enum Singleton{
INSTANCE;
}
你应该坚持使用其中一个
You should probably stick with one of these
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