java.util.concurrent.Lock
1、Lock比传统线程模型中的synchronized方式更加面向对象，与生活中的锁类似，
锁本身也应该是一个对象。两个线程执行的代码片段要实现同步互斥的效果，它们必须用同一个Lock对象。
lock替代synchronized
class Outputer {
Lock lock = new ReentrantLock();
public void output(String name) {
int len = name.length();
lock.lock();
try{
for (int i = 0; i < len; i++) {
char c = name.charAt(i);
System.out.print(c);
}
}finally{
lock.unlock(); //这里防止内部代码出现异常，即无论如何最后都会释放锁
}
lock.unlock();
System.out.println();
}
}
售票系统
package com.java.juc; import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock; public class TestLock { public static void main(String[] args) {
Ticket ticket = new Ticket();
new Thread(ticket, "窗口1售票").start();
new Thread(ticket, "窗口2售票").start();
new Thread(ticket, "窗口3售票").start();
} } class Ticket implements Runnable {
private int ticket = 100;
private Lock lock = new ReentrantLock(); @Override
public void run() {
while (true) {
lock.lock();
try {
if (ticket > 0) {
Thread.sleep(20);
System.out.println(Thread.currentThread().getName()
+ "，余票量：" + ticket--);
}
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
}
2、读写锁：
读写锁：分为读锁和写锁，多个读锁不互斥，读锁与写锁互斥，这是由jvm自己控制的，你只要上好相应的锁即可。
* 如果你的代码只读数据，可以很多人同时读，但不能同时写，那就上读锁；
* 如果你的代码修改数据，只能有一个人在写，且不能同时读取，那就上写锁。
* 总之，读的时候上读锁，写的时候上写锁！
/* 面试题：3个线程读，3个线程写 同一个数据
*/
public class ReadWriteLockTest {
public static void main(String[] args) {
final Queue3 queue = new Queue3(); for(int i = 0;i<3;i++){
new Thread(new Runnable() {
@Override
public void run() {
while(true){
queue.get();
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
queue.set(new Random().nextInt(10000));
}
}).start();
}
} } class Queue3{
private Object data = null; //共享数据 ，只能有一个线程写该数据，但可以有多个线程同时读
ReadWriteLock rwl = new ReentrantReadWriteLock(); //读写锁 public void get(){
try {
rwl.readLock().lock(); //上读锁 可以有多个线程同时读
System.out.println(Thread.currentThread().getName() + " be ready to read data!");
Thread.sleep((long)Math.random() * 1000);
System.out.println(Thread.currentThread().getName() + " have read data : "+ data);
} catch (InterruptedException e) {
}finally{
rwl.readLock().unlock(); //释放读锁
}
}
public void set(Object data){
try {
rwl.writeLock().lock(); //添加写锁，保证只能有一个线程进行写操作
System.out.println(Thread.currentThread().getName() + " be read to write data: "+ data);
Thread.sleep((long)Math.random() * 1000);
this.data = data;
System.out.println(Thread.currentThread().getName() + "has write data");
} catch (InterruptedException e) {
e.printStackTrace();
}finally{
rwl.writeLock().unlock(); //释放写锁
}
}
}
简单的读写锁示例
package com.java.juc; import java.util.Random;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock; public class TestReadWriteLock {
public static void main(String[] args) {
final ReadWriteLockDemo demo = new ReadWriteLockDemo();
new Thread(new Runnable(){
@Override
public void run() {
demo.set(new Random().nextInt(5000));
}
},"Write").start(); for(int i = 0;i<100;i++){
new Thread(new Runnable() {
@Override
public void run() {
demo.get();
}
}, "Read").start();
}
}
} class ReadWriteLockDemo{
private int number = 0; private ReadWriteLock lock = new ReentrantReadWriteLock(); public void get(){
try{
lock.readLock().lock();
System.out.println(Thread.currentThread().getName() +" "+number);
}finally{
lock.readLock().unlock();
}
}
public void set(int number){
try{
lock.writeLock().lock();
this.number = number;
}finally{
lock.writeLock().unlock();
}
}
}
Hibernate的一个面试题：
User user = session.load(id,User.class);
User user = session.get(id,User.class);
以上两个的却别。
get()方式，直接查询数据库，如果查询到赋值给User对象，如果没有查询到则返回为null
load()方式，实际上是从User的一个代理中获取， User$Proxy中包含有一个真实的User对象，当调用load()时，如果成员变量User为null，则从数据库查询将记录返回并给User赋值，当load()时User不为null，则直接返回User对象
/**
* 面试题： 设计一个缓存系统
* @author Administrator
*
*/
public class CacheDemo { Map<String, Object> cache = new HashMap<String, Object>();
public static void main(String[] args) { } private ReadWriteLock rwl = new ReentrantReadWriteLock();
public Object getData(String key){
rwl.readLock().lock();
Object value = null;
try {
value = cache.get(key);
if(value == null){
rwl.readLock().unlock();
rwl.writeLock().lock();
try {
if(value == null){ //防止后边线程加载数据，使用双端检测机制
value = "xxx"; //queryDB
cache.put(key, value);
}
}finally{
rwl.writeLock().unlock();
}
rwl.readLock().lock();
}
} catch (Exception e) {
}finally{
rwl.readLock().unlock();
}
return value;
} }
ReadWriteLock javaAPI中有缓存的代码：
class CachedData {
Object data;
volatile boolean cacheValid;
ReentrantReadWriteLock rwl = new ReentrantReadWriteLock();
void processCachedData() {
rwl.readLock().lock();
if (!cacheValid) {
// Must release read lock before acquiring write lock
rwl.readLock().unlock();
rwl.writeLock().lock();
// Recheck state because another thread might have acquired
// write lock and changed state before we did.
if (!cacheValid) {
data = ...
cacheValid = true;
}
// Downgrade by acquiring read lock before releasing write lock
rwl.readLock().lock();
rwl.writeLock().unlock(); // Unlock write, still hold read
}
use(data);
rwl.readLock().unlock();
}
}
3、Condition 实现线程通信
传统的线程通信方式
/*
* 传统线程通信
* 主线程和子线程分别打印 100次 和 10次，循环50次
*/
public class TraditionalThreadCommunication2 { public static void main(String[] args) {
final Buiness buiness = new Buiness();
new Thread(new Runnable() {
@Override
public void run() {
for(int i = 1;i<=50;i++){
buiness.sub(i);
}
}
}).start(); for(int i = 1;i<=50;i++){
buiness.main(i);
}
} static class Buiness{
private boolean isShouldSub = false; //主线程先打印
public synchronized void main(int j){ //进行同步，防止在打印时被其他线程干扰
while(isShouldSub){ //这里使用while 防止假唤醒
try {
this.wait(); //wait() 和 notify() 必须出现在synchronized同步中
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for(int i = 1;i<=100;i++){
System.out.println("main thread print "+ i + " loop of " + j);
}
isShouldSub = true;
this.notify();
}
public synchronized void sub(int j){
while(!isShouldSub){
try {
this.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for(int i = 1 ; i<=10;i++){
System.out.println("sub thread print "+ i + " loop of " + j);
}
isShouldSub = false;
this.notify();
}
} }
将上述程序改写为使用Condition
/*
* 传统线程通信
* 主线程和子线程分别打印 100次 和 10次，循环50次
* 改写成使用 Condition 的方式
*/
public class TraditionalThreadCommunication2 { public static void main(String[] args) {
final Buiness buiness = new Buiness();
new Thread(new Runnable() {
@Override
public void run() {
for(int i = 1;i<=50;i++){
buiness.sub(i);
}
}
}).start(); for(int i = 1;i<=50;i++){
buiness.main(i);
}
} /**
* 将程序改写为使用Lock&Condition的方式进行 同步和通信
* @author Administrator
*
*/
static class Buiness{
Lock lock = new ReentrantLock();
Condition condition = lock.newCondition();
private boolean isShouldSub = false; //主线程先打印
public void main(int j){ //进行同步，防止在打印时被其他线程干扰
lock.lock();
try {
while(isShouldSub){ //这里使用while 防止假唤醒
try {
condition.await();
// this.wait(); //wait() 和 notify() 必须出现在同步监视器内部中
} catch (Exception e) {
e.printStackTrace();
}
}
for(int i = 1;i<=100;i++){
System.out.println("main thread print "+ i + " loop of " + j);
}
isShouldSub = true;
condition.signal();
// this.notify();
} finally {
lock.unlock();
}
}
public void sub(int j){
lock.lock();
try {
while(!isShouldSub){
try {
condition.await();
// this.wait();
} catch (Exception e) {
e.printStackTrace();
}
}
for(int i = 1 ; i<=10;i++){
System.out.println("sub thread print "+ i + " loop of " + j);
}
isShouldSub = false;
condition.signal();
// this.notify();
} finally{
lock.unlock();
}
}
} }
main thread print 1 loop of 1
main thread print 2 loop of 1
main thread print 3 loop of 1
main thread print 4 loop of 1
main thread print 5 loop of 1
main thread print 6 loop of 1
main thread print 7 loop of 1
...
main thread print 99 loop of 1
main thread print 100 loop of 1
sub thread print 1 loop of 1
sub thread print 2 loop of 1
sub thread print 3 loop of 1
sub thread print 4 loop of 1
sub thread print 5 loop of 1
sub thread print 6 loop of 1
sub thread print 7 loop of 1
sub thread print 8 loop of 1
sub thread print 9 loop of 1
sub thread print 10 loop of 1
main thread print 1 loop of 2
main thread print 2 loop of 2
main thread print 3 loop of 2
main thread print 4 loop of 2
main thread print 5 loop of 2
main thread print 6 loop of 2
main thread print 7 loop of 2
main thread print 8 loop of 2
main thread print 9 loop of 2
...
main thread print 99 loop of 2
main thread print 100 loop of 2
sub thread print 1 loop of 2
sub thread print 2 loop of 2
sub thread print 3 loop of 2
sub thread print 4 loop of 2
sub thread print 5 loop of 2
sub thread print 6 loop of 2
sub thread print 7 loop of 2
sub thread print 8 loop of 2
sub thread print 9 loop of 2
sub thread print 10 loop of 2
main thread print 1 loop of 3
main thread print 2 loop of 3
main thread print 3 loop of 3
...
使用Condition比传统的好处
可以实现多路Condition ，在javaAPI中有
class BoundedBuffer {
final Lock lock = new ReentrantLock();
final Condition notFull = lock.newCondition();
final Condition notEmpty = lock.newCondition();
final Object[] items = new Object[100];
int putptr, takeptr, count;
public void put(Object x) throws InterruptedException {
lock.lock();
try {
while (count == items.length)
notFull.await();
items[putptr] = x;
if (++putptr == items.length) putptr = 0;
++count;
notEmpty.signal();
} finally {
lock.unlock();
}
}
public Object take() throws InterruptedException {
lock.lock();
try {
while (count == 0)
notEmpty.await();
Object x = items[takeptr];
if (++takeptr == items.length) takeptr = 0;
--count;
notFull.signal();
return x;
} finally {
lock.unlock();
}
}
}
使用多路Condition，可以扩展上述的一个例子，老大打印完 -> 老二 老二-> 老三 老三-> 老大 老大-> 老二...
/**
* 第一个线程循环100次，第二个线程循环10次，第三个线程循环20次，如此循环50次，请写出程序 这里使用Condition
*
* @author Administrator
*
*/
public class ThreeConditionCommunication { public static void main(String[] args) {
final Business2 business = new Business2();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 1; i <= 50; i++) {
business.sub2(i);
}
}
}).start();
new Thread(new Runnable() {
@Override
public void run() {
for (int i = 1; i <= 50; i++) {
business.sub3(i);
}
}
}).start(); for (int i = 1; i <= 50; i++) {
business.main(i);
}
} } class Business2 {
Lock lock = new ReentrantLock();
Condition condition1 = lock.newCondition();
Condition condition2 = lock.newCondition();
Condition condition3 = lock.newCondition();
private int shoudeSub = 1; public void sub2(int i) {
lock.lock();
try {
while (shoudeSub != 2) { // 这里也可以用 if ，用while比较好一些 As in the one argument
// version, interrupts and spurious wakeups are
// possible, and this method should always be
// used in a loop
try { // 防止线程有可能被假唤醒 (while放在这里提现了水准)
condition2.await(); //等待
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for (int j = 1; j <= 100; j++) {
System.out.println("sub2 thread sequence of " + j + ", loop of " + i);
}
shoudeSub = 3;
condition3.signal();//唤醒
} finally{
lock.unlock();
}
}
public void sub3(int i) {
lock.lock();
try {
while (shoudeSub != 3) { // 这里也可以用 if ，用while比较好一些 As in the one argument
// version, interrupts and spurious wakeups are
// possible, and this method should always be
// used in a loop
try { // 防止线程有可能被假唤醒 (while放在这里提现了水准)
condition3.await(); //等待
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for (int j = 1; j <= 20; j++) {
System.out.println("sub3 thread sequence of " + j + ", loop of " + i);
}
shoudeSub = 1;
condition1.signal();//唤醒
} finally{
lock.unlock();
}
} public void main(int i) {
lock.lock();
try {
while (shoudeSub != 1) {
try {
condition1.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
for (int j = 1; j <= 10; j++) {
System.out.println("main thread sequence of " + j + ", loop of "
+ i);
}
shoudeSub = 2;
condition2.signal();
} finally{
lock.unlock();
}
}
/**
*
* synchronized (obj) { 这里的obj与obj.wait必须相同，否则会抛异常 while (<condition does
* not hold>) obj.wait(); ... // Perform action appropriate to condition }
*/
}
Condition的一个例子：
编写一个程序，开启3个线程 ，这三个线程的ID分别为 A，B, C,每个线程将自己的ID 在屏幕上打印10遍，要求输出的结果必须按顺序显示。
如：ABCABCABC.....依次递归
这里实现了一个比题目稍微难得例子，A 打印10次，B打印20次 ，C打印5次依次递归20次。
package com.java.juc; import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock; public class TestAlternative { public static void main(String[] args) {
final Alternative alternative = new Alternative();
new Thread(new Runnable(){
@Override
public void run() {
for(int i = 1;i<=20;i++){
alternative.loopA(i);
}
}
},"A").start();
new Thread(new Runnable(){
@Override
public void run() {
for(int i = 1;i<=20;i++){
alternative.loopB(i);
}
}
},"B").start();
new Thread(new Runnable(){
@Override
public void run() {
for(int i = 1;i<=20;i++){
alternative.loopC(i);
System.out.println("-----------------");
}
}
},"C").start(); } } class Alternative{ private int number = 1;
private Lock lock = new ReentrantLock();
private Condition condition1 = lock.newCondition();
private Condition condition2 = lock.newCondition();
private Condition condition3 = lock.newCondition(); void loopA(int outerLoop){
lock.lock();
try{
while(number != 1){
condition1.await();
}
for(int i = 1;i<=10;i++){
System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + outerLoop);
}
number = 2;
condition2.signal();
}catch(Exception e){
}finally {
lock.unlock();
}
} void loopB(int outerLoop){
lock.lock();
try{
while(number != 2){
condition2.await();
}
for(int i = 1;i<=20;i++){
System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + outerLoop);
}
number = 3;
condition3.signal();
}catch(Exception e){ }finally{
lock.unlock();
}
}
void loopC(int outerLoop){
lock.lock();
try{
while(number != 3){
condition3.await();
}
for(int i = 1;i<=5;i++){
System.out.println(Thread.currentThread().getName() + "\t" + i + "\t" + outerLoop);
}
number = 1;
condition1.signal();
}catch(Exception e){ }finally{
lock.unlock();
}
}
}
java5的Semaphere同步工具
Semaphore实现信号灯
Semaphore可以维护当前访问自身的线程个数，并提供了同步机制。使用Semaphore可以控制同时访问资源的线程个数，例如，实现一个文件允许的并发访问数。
假设一个文件同时可以被3个人访问，来了5个人，同时只有3个访问。3个中任何一个出来后，等待的就可以进去了。
public class SemaphoreTest {
public static void main(String[] args) {
ExecutorService service = Executors.newCachedThreadPool();
final Semaphore sp = new Semaphore(3); //还有一个构造方法，Semaphore(int permits, boolean fair) fair参数为true表示谁先来谁先进，一种公平的原则
for(int i=0;i<10;i++){
Runnable runnable = new Runnable(){
public void run(){
try {
sp.acquire();
} catch (InterruptedException e1) {
e1.printStackTrace();
}
System.out.println("线程" + Thread.currentThread().getName() +
"进入，当前已有" + (3-sp.availablePermits()) + "个并发");
try {
Thread.sleep((long)(Math.random()*10000));
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("线程" + Thread.currentThread().getName() +
"即将离开");
sp.release();
//下面代码有时候执行不准确，因为其没有和上面的代码合成原子单元
System.out.println("线程" + Thread.currentThread().getName() +
"已离开，当前已有" + (3-sp.availablePermits()) + "个并发");
}
};
service.execute(runnable);
}
}
}
单个信号量的Semaphore对象可以实现互斥锁的功能，并且可以是由一个线程获得了 "锁"，再由另外一个线程释放"锁"，这可应用于死锁恢复的一些场合。
java5 的CyclicBarrier同步工具
/**
* 表示大家彼此等待，大家集合好后才开始出发，分散活动后又在指定地点集合碰面，
* 这就好比整个公司的人员利用周末时间集体郊游一样，先各自从家出发到公司集合后，
* 再同时出发到公园游玩，在指定地点集合后再同时开始就餐，…。
* @author Administrator
*
*/
public class CyclicBarrierTest { public static void main(String[] args) {
ExecutorService threadPool = Executors.newCachedThreadPool();
final CyclicBarrier cb = new CyclicBarrier(3);
for (int i = 0; i < 3; i++) {
Runnable runnable = new Runnable() {
public void run() {
try {
Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程"+ Thread.currentThread().getName()
+ "即将到达集合点1,当前已有 "+(cb.getNumberWaiting()+1) +"个已经到达，"+(cb.getNumberWaiting() == 2?"都到齐了，继续走啊":"正在等待"));
cb.await(); Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程"+ Thread.currentThread().getName()
+ "即将到达集合点2,当前已有 "+(cb.getNumberWaiting()+1) +"个已经到达，"+(cb.getNumberWaiting() == 2?"都到齐了，继续走啊":"正在等待"));
cb.await(); Thread.sleep((long) (Math.random() * 10000));
System.out.println("线程"+ Thread.currentThread().getName()
+ "即将到达集合点3,当前已有 "+(cb.getNumberWaiting()+1) +"个已经到达，"+(cb.getNumberWaiting() == 2?"都到齐了，继续走啊":"正在等待"));
cb.await();
} catch (Exception e) {
// TODO: handle exception
}
}
};
threadPool.execute(runnable);
}
threadPool.shutdown();
} }
java5的CountDownLatch同步工具
CountDownLatch : 闭锁，在完成某些运算时，只有其他所有线程的运算全部完成，当前运算才继续执行
CountDownLatch应用1：比如要统计5个线程并发的运行时间，即线程的开始时间与最后一个线程的运行结束时间的间隔时间。
package com.java.juc;
import java.util.concurrent.CountDownLatch;
public class TestCountDownLatch2 {
public static void main(String[] args) {
CountDownLatch latch = new CountDownLatch(5);
LatchDemo2 ld = new LatchDemo2(latch);
long start = System.currentTimeMillis();
for(int i = 0;i<5;i++){
new Thread(ld).start();
}
try {
latch.await(); //先执行完成的线程需要等待还没有执行完的线程
} catch (InterruptedException e) {
e.printStackTrace();
}
long end = System.currentTimeMillis();
System.out.println("cost: "+ (end - start));
}
}
class LatchDemo2 implements Runnable{
private CountDownLatch latch;
public LatchDemo2(CountDownLatch latch) {
this.latch = latch;
}
@Override
public void run() {
try {
synchronized(this){
for(int i = 0;i<50000;i++){ //找出50000以内的所有偶数
if(i % 2 == 0){
System.out.println(i);
}
}
}
} finally{
latch.countDown(); //为了让这一句一定执行可以放在finally中
}
}
}
还可以应用于计算所有种类商品的平均销售总和，平均销售时间等，如果使用单线程计算效率非常低，相当于是串行计算。可以使用并行计算，按照商品种类进行区分并行的计算。可以将最终的每个线程的计算结果在进行汇总，可以得出最终的的总的销售数据，这就可以使用CountDownLatch进行操作，可以大幅度提高效率。(京东)
应用:运动员跑步比赛，得到最终的排名需要在所有运动员都完成之后，公布最终的结果。
/**
* 犹如倒计时计数器，调用CountDownLatch对象的countDown方法就将计数器减一，
* 当计数器到达0时，则所有等待者或单个等待者开始执行。
* 可以实现一个人（也可以是多个人）等待其他所有人都来通知他，可以实现一个人通知多个人的效果，
* 类似裁判一声口令，运动员同时开始奔跑，或者所有运动员都跑到
* 终点后裁判才可以公布结果。还可以实现一个计划需要多个领导都签字后
* 才能继续向下实施的情况
* @author Administrator
*
*/
public class CountDownLetchTest { public static void main(String[] args) {
ExecutorService executorService = Executors.newCachedThreadPool();
final CountDownLatch cdOrder = new CountDownLatch(1); //计数器初始值 1
final CountDownLatch cdAnswer = new CountDownLatch(3);
for(int i = 0;i<3;i++){
Runnable runnable = new Runnable() { @Override
public void run() {
try {
System.out.println("线程"+Thread.currentThread().getName()
+"正准备接受命令");
cdOrder.await();
System.out.println("线程"+Thread.currentThread().getName()
+"已接受命令");
Thread.sleep((long)(Math.random()*10000));
System.out.println("线程"+Thread.currentThread().getName()
+"回应命令处理结果");
cdAnswer.countDown();
} catch (Exception e) {
// TODO: handle exception
}
}
};
executorService.execute(runnable);
}
try {
Thread.sleep((long)(Math.random()*10000));
System.out.println("线程"+Thread.currentThread().getName()
+"即将发布命令");
cdOrder.countDown(); //计数器数值减 1
System.out.println("线程"+Thread.currentThread().getName()
+"已发送命令，正在等待结果");
cdAnswer.await();
System.out.println("线程"+Thread.currentThread().getName()
+"已收到所有响应结果");
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
executorService.shutdown();
}
}
java 中CycliBarriar 和 CountDownLatch 有什么区别？
这两个的区别是CyclicBarrier 可以重复使用已经通过的障碍，而 CountdownLatch 不能重复使用。
java5的Exchanger同步工具
/**
* 用于实现两个人之间的数据交换，每个人在完成一定的事物后想与对方交换数据，第一个先拿出数据的人将
* 一直等待第二个人拿着数据到来时，才能彼此交换数据。
* @author Administrator
*
*/
public class ExchangerTest { public static void main(String[] args) {
ExecutorService executorService = Executors.newCachedThreadPool();
final Exchanger exchanger = new Exchanger();
executorService.execute(new Runnable() { @Override
public void run() {
try {
String data1 = "aaa";
System.out.println("线程" + Thread.currentThread().getName()
+ "正在把数据" + data1 + "换出去");
Thread.sleep((long) (Math.random() * 10000));
String data2 = (String) exchanger.exchange(data1);
System.out.println("线程" + Thread.currentThread().getName()
+ "换回的数据为 " + data2);
} catch (Exception e) {
// TODO: handle exception
}
}
});
executorService.execute(new Runnable() { @Override
public void run() {
try {
String data1 = "bbb";
System.out.println("线程" + Thread.currentThread().getName()
+ "正在把数据" + data1 + "换出去");
Thread.sleep((long) (Math.random() * 10000));
String data2 = (String) exchanger.exchange(data1);
System.out.println("线程" + Thread.currentThread().getName()
+ "换回的数据为 " + data2);
} catch (Exception e) {
// TODO: handle exception
}
}
});
} }
打印结果为：
线程 pool-1-thread-1正把数据 aaa 换出去
线程 pool-1-thread-2正把数据 bbb 换出去
线程 pool-1-thread-2换回的数据为 aaa
线程 pool-1-thread-1换回的数据为 bbb