ConditionObject
| 属性 | 说明 |
| Node firstWaiter | 头节点 |
| Node lastWaiter | 尾节点 |
为Condition接口实现,Condition的目的主要是替代Object的wait,notify,notifyAll方法的,它是基于Lock实现的.(而Lock是来替代synchronized方法).
结构
使用时序图
关键方法
阻塞线程:await
对应Object.wait(),通过AQS机制释放锁定的资源,终止当前线程,恢复后使用AQS独占模式重新锁定资源
acquireQueued:此时node节点已转换为AQS中节点
public final void await() throws InterruptedException { if (Thread.interrupted()) throw new InterruptedException(); Node node = addConditionWaiter(); long savedState = fullyRelease(node); int interruptMode = 0; while (!isOnSyncQueue(node)) { LockSupport.park(this); if ((interruptMode = checkInterruptWhileWaiting(node)) != 0) break; } if (acquireQueued(node, savedState) && interruptMode != THROW_IE) interruptMode = REINTERRUPT; if (node.nextWaiter != null) // clean up if cancelled unlinkCancelledWaiters(); if (interruptMode != 0) reportInterruptAfterWait(interruptMode); }
唤醒线程:signal
transferForSignal转换节点后await()中acquireQueued(node,savedState)操作的节点已是AQS中的节点
isHeldExclusively:子类实现.判断是否独家持有
public final void signal() { if (!isHeldExclusively()) throw new IllegalMonitorStateException(); Node first = firstWaiter; if (first != null) doSignal(first); }
