1、Condition介绍1.1 Condition是对线程的wait,notify的增强1.2 在ReentrantLock中他的实现类是AQS中的ConditionObject，实现了Condition接口,利用AQS的节点，实现了条件队列。

2、案例分析2.1 说明：Thread-1获取锁，然后await，释放锁；Thread-2获得锁，唤醒Thread-1，释放锁；Thread-1重新获取锁，释放锁。2.2 代码2.2.1 Thread-1

import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;public class Task1 implements Runnable{ private ReentrantLock lock; private Condition con; public Task1(ReentrantLock lock, Condition con) { this.lock = lock; this.con = con; } @Override public void run() { try { lock.lock(); System.out.println(Thread.currentThread().getName() + "获取到锁...."); System.out.println(Thread.currentThread().getName() + "开始阻塞...."); con.await(); System.out.println(Thread.currentThread().getName() + "重新获取锁，继续执行...."); Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } finally { System.out.println(Thread.currentThread().getName() + "释放锁...."); lock.unlock(); } }}2.2.2 Thread-2

import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;public class Task2 implements Runnable{ private ReentrantLock lock; private Condition con; public Task2(ReentrantLock lock, Condition con) { this.lock = lock; this.con = con; } @Override public void run() { try { lock.lock(); System.out.println(Thread.currentThread().getName() + "获取到锁...."); System.out.println(Thread.currentThread().getName() + "唤醒Thread-1...."); con.signal(); Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } finally { System.out.println(Thread.currentThread().getName() + "释放锁...."); lock.unlock(); } }}2.2.3 启动文件

import java.text.ParseException;import java.util.concurrent.locks.Condition;import java.util.concurrent.locks.ReentrantLock;public class Main { public static void main(String[] args) throws ParseException, InterruptedException { ReentrantLock lock = new ReentrantLock(true); Condition condition = lock.newCondition(); Thread t1 = new Thread(new Task1(lock,condition),"Thread-1"); Thread.sleep(2000); Thread t2 = new Thread(new Task2(lock,condition),"Thread-2"); t1.start(); t2.start(); }}2.2.4 运行结果

3、源码分析3.1 获取锁的源码在上一篇已经分析过了，来看await操作：

public final void await() throws InterruptedException { if (Thread.interrupted()) throw new InterruptedException(); //判断线程是否中断，中断则抛出异常 Node node = addConditionWaiter(); //当前线程包装节点，放入【条件对列】，注意不是【等待队列】 int savedState = fullyRelease(node);//释放锁资源 int interruptMode = 0; while (!isOnSyncQueue(node)) { //如果当前节点不在【等待队列】 LockSupport.park(this); //在这里阻塞，等待被唤醒，后面代码唤醒前不执行 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); }3.1.1 await()方法会释放当前线程持有的锁，就是fullyRelease方法的作用

3.1.2 线程A释放了锁，并进入条件对列，处于阻塞状态。3.2 Thread-2获取到锁后，调用signal方法唤醒Thread-1

final boolean transferForSignal(Node node) { /* * If cannot change waitStatus, the node has been cancelled. */ //将节点的状态修改为0，从【条件队列】节点状态转换为【等待队列】默认节点状态0,节点可以插入【等待队列】 if (!compareAndSetWaitStatus(node, Node.CONDITION, 0)) return false; /* * Splice onto queue and try to set waitStatus of predecessor to * indicate that thread is (probably) waiting. If cancelled or * attempt to set waitStatus fails, wake up to resync (in which * case the waitStatus can be transiently and harmlessly wrong). */ Node p = enq(node);//将节点插入【等待队列】 int ws = p.waitStatus; if (ws > 0 || !compareAndSetWaitStatus(p, ws, Node.SIGNAL)) //将前驱节点设置为可唤醒状态 LockSupport.unpark(node.thread);//唤醒节点，也就是Thread-1 return true; }3.3 Thread-2释放锁3.3.1Thread-2释放锁，会唤醒【等待队列】的首节点，参看上一篇介绍（unparkSuccessor方法）3.3.2 Thread-1继续执行