Instead of double - checked locking , use the initialize - on - demand holder class idiom , which provides lazy initialization , is thread - safe , and is faster and less confusing than double - checked locking 不使用双重检查锁定，而使用initialize - on - demand holder class idiom ，它提供了迟缓初始化，是线程安全的，而且比双重检查锁定更快且没那么混乱：
It is worth noting that broken techniques like double - checked locking are still broken under the new memory model , and that " fixing " double - checked locking was not one of the goals of the new memory model effort 值得注意的是，有漏洞的技术（如双重检查锁定）在新的内存模型下仍然有漏洞，并且“修复”双重检查锁定技术并不是新内存模型所致力的一个目标。
The whole point of double - checked locking was that it was supposed to be a performance optimization , designed to eliminate synchronization on the common code path , largely because synchronization was relatively expensive in very early jdks 双重检查锁定的要点是，它假定是性能优化的，设计用于消除公共代码路径的同步，很大程度上因为对于早期的jdk来说，同步是相对昂贵的。
Under the old memory model , this did not render double - checked locking thread - safe , because writes to a volatile field could still be reordered with writes to other nonvolatile fields such as the fields of the newly constructed object , and therefore the volatile instance reference could still hold a reference to an incompletely constructed object 。 ）在旧的内存模型中，这不能使双重检查锁定成为线程安全的，因为对volatile字段的写仍然会与对其他nonvolatile字段的写（如新构造的对象的字段）一起重新排序，因而volatile实例引用仍然可能包含对一个未构造完的对象的引用。
