java 之 AtomicReference
AtomicReference类提供了一个可以原子读写的对象引用变量。 原子意味着尝试更改相同AtomicReference的多个线程（例如，使用比较和交换操作）不会使AtomicReference最终达到不一致的状态。 AtomicReference甚至有一个先进的compareAndSet（）方法，它可以将引用与预期值（引用）进行比较，如果它们相等，则在AtomicReference对象内设置一个新的引用。
创建一个AtomicReference
AtomicReference atomicReference = new AtomicReference();
String initialReference = "the initially referenced string";
AtomicReference atomicReference = new AtomicReference(initialReference);
创建一个类型的AtomicReference
AtomicReference<String> atomicStringReference = new AtomicReference<String>();
获取值
AtomicReference atomicReference = new AtomicReference("first value referenced");
String reference = (String) atomicReference.get();
赋值
AtomicReference atomicReference =
new AtomicReference();
atomicReference.set("New object referenced");
比较赋值
String initialReference = "initial value referenced";
AtomicReference<String> atomicStringReference =
new AtomicReference<String>(initialReference);
String newReference = "new value referenced";
boolean exchanged = atomicStringReference.compareAndSet(initialReference, newReference);
System.out.println("exchanged: " + exchanged);
exchanged = atomicStringReference.compareAndSet(initialReference, newReference);
System.out.println("exchanged: " + exchanged);
