public
class Singleton {
// Private constructor prevents instantiation from other classes
private Singleton() { }
/**
* SingletonHolder is loaded on the first execution of Singleton.getInstance()
* or the first access to SingletonHolder.INSTANCE, not before.
*/
private static class SingletonHolder {
public static final Singleton INSTANCE = new Singleton();
}
public static Singleton getInstance() {
return SingletonHolder.INSTANCE;
}
}
// Private constructor prevents instantiation from other classes
private Singleton() { }
/**
* SingletonHolder is loaded on the first execution of Singleton.getInstance()
* or the first access to SingletonHolder.INSTANCE, not before.
*/
private static class SingletonHolder {
public static final Singleton INSTANCE = new Singleton();
}
public static Singleton getInstance() {
return SingletonHolder.INSTANCE;
}
}
99%的Java程序員實現不了一個完美的單例模式，看看Wiki上給出的最佳實現：http://t.cn/zOvZMy3 通過單例模式全面了解Double-checked locking以及並發時候的鎖的問題：http://t.cn/aKbmIb
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