Java线程通讯方式
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线程间通信常用方式如下：
l 休眠唤醒方式：
Object的wait、notify、notifyAll
Condition的await、signal、signalAll
l CountDownLatch：用于某个线程A等待若干个其他线程执行完之后，它才执行
l CyclicBarrier：一组线程等待至某个状态之后再全部同时执行
l Semaphore：用于控制对某组资源的访问权限
Object的wait、notify、notifyAll
public class WaitNotifyRunnable{
private Object obj = new Object();
private Integer i=0;
public void odd() {
while(i<10){
synchronized (obj){
if(i%2 == 1){
System.out.println("奇数："+i);
i++;
obj.notify();
} else {
try {
obj.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
public void even(){
while(i<10){
synchronized (obj){
if(i%2 == 0){
System.out.println("偶数："+i);
i++;
obj.notify();
} else {
try {
obj.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
}
}
public static void main(String[] args){
final WaitNotifyRunnable runnable = new WaitNotifyRunnable();
Thread t1 = new Thread(new Runnable() {
public void run() {
runnable.odd();
}
}, "偶数线程");
Thread t2 = new Thread(new Runnable() {
public void run() {
runnable.even();
}
}, "奇数线程");
t1.start();
t2.start();
}
}
Condition的await、signal、signalAll
import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;
public class WaitNotifyRunnable{
private Lock lock = new ReentrantLock();
private Condition condition = lock.newCondition();
private Integer i=0;
public void odd() {
while(i<10){
lock.lock();
try{
if(i%2 == 1){
System.out.println("奇数："+i);
i++;
condition.signal();
} else {
condition.await();
}
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
public void even(){
while(i<10){
lock.lock();
try{
if(i%2 == 0){
System.out.println("偶数："+i);
i++;
condition.signal();
} else {
condition.await();
}
} catch (InterruptedException e) {
e.printStackTrace();
} finally {
lock.unlock();
}
}
}
public static void main(String[] args){
final WaitNotifyRunnable runnable = new WaitNotifyRunnable();
Thread t1 = new Thread(new Runnable() {
public void run() {
runnable.odd();
}
}, "偶数线程");
Thread t2 = new Thread(new Runnable() {
public void run() {
runnable.even();
}
}, "奇数线程");
t1.start();
t2.start();
}
}
Object和Condition休眠唤醒区别
l object wait()必须在synchronized（同步锁）下使用，
l object wait()必须要通过Nodify()方法进行唤醒
l condition await() 必须和Lock（互斥锁/共享锁）配合使用
l condition await() 必须通过 signal() 方法进行唤醒
CountDownLatch方式
CountDownLatch这个类能够使一个线程等待其他线程完成各自的工作后再执行。
CountDownLatch是通过一个计数器来实现的，计数器的初始值为线程的数量
每当一个线程完成了自己的任务后，计数器的值就会减1。当计数器值到达0时，它表示所有的线程已经完成了任务，然后在闭锁上等待的线程就可以恢复执行任务
import java.util.concurrent.CountDownLatch;
public class CoachRecerDemo {
private CountDownLatch countDownLatch=new CountDownLatch(3); //设置要等待的运动员
//运动员方法
public void racer(){
//获取线程名
String name=Thread.currentThread().getName();
System.out.println(name+"正在准备....");
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(name+"准备完毕");
countDownLatch.countDown();//-1
}
//教练方法
public void coach(){
String name=Thread.currentThread().getName();
System.out.println(name+"等待运动员准备...");
try {
countDownLatch.await();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("所有运动员就绪，"+name+"开始训练");
}
public static void main(String[] args) {
//1.创建CoachRecerDemo 实例
CoachRecerDemo coachRecerDemo=new CoachRecerDemo();
//2.创建三个线程对象
Thread thread1=new Thread(new Runnable(){
public void run() {
coachRecerDemo.racer();
}
},"运动员1");
Thread thread2=new Thread(new Runnable() {
public void run() {
coachRecerDemo.racer();
}
},"运动员2");
Thread thread3=new Thread(new Runnable() {
public void run() {
coachRecerDemo.racer();
}
},"运动员3");
//3.教练
Thread thread4=new Thread(new Runnable() {
public void run() {
coachRecerDemo.coach();
}
},"教练");
thread4.start();
thread1.start();
thread2.start();
thread3.start();
}
}
CyclicBarrier方式
CyclicBarrier是在java1.5被引入的，存在于java.util.concurrent包下。
CyclicBarrier实现让一组线程等待至某个状态之后再全部同时执行。
CyclicBarrier底层是三个线程同时启动
import java.util.Date;
import java.util.concurrent.BrokenBarrierException;
import java.util.concurrent.CyclicBarrier;
public class ThreeThreadStartDemo {
private CyclicBarrier cyclicBarrier = new CyclicBarrier(3);// 所有参与启动的线程数
public void startThread() {
// 打印线程准备启动
String name = Thread.currentThread().getName();
System.out.println(name + "正在准备...");
// 2.调用CyclicBarriar的await方法等待线程准备完毕
try {
cyclicBarrier.await();
} catch (InterruptedException | BrokenBarrierException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
// 3.打印线程启动信息
System.out.println(name + "已经启动完毕" + new Date().getTime());
}
public static void main(String[] args) {
final ThreeThreadStartDemo threadStartDemo = new ThreeThreadStartDemo();
Thread thread1 = new Thread(new Runnable() {
public void run() {
threadStartDemo.startThread();
}
});
Thread thread2 = new Thread(new Runnable() {
public void run() {
threadStartDemo.startThread();
}
});
Thread thread3 = new Thread(new Runnable() {
public void run() {
threadStartDemo.startThread();
}
});
thread1.start();
thread2.start();
thread3.start();
}
}
Semaphore方式
Semaphore是在java1.5被引入的，存在于java.util.concurrent包下。
Semaphore用于控制对某组资源的访问权限。
import java.util.concurrent.Semaphore;
public class WorkerMachineDemo {
static class Work implements Runnable {
private int workerNum;
private Semaphore semaphore;
public Work(int workerNum, Semaphore semaphore) {
this.workerNum = workerNum;
this.semaphore = semaphore;
}
public void run() {
// 1.获取机器
// 2.打印工人获取到机器，开始工作
// 3.线程睡眠1000毫秒
// 4.使用完毕
try {
semaphore.acquire();
String name = Thread.currentThread().getName();
System.out.println(name + "获取到机器，开始工作");
Thread.sleep(1000);
semaphore.release();
System.out.println(name + "使用完毕，释放机器！");
} catch (Exception e) {
// TODO: handle exception
}
}
}
public static void main(String[] args) {
int works = 8;
Semaphore semaphore = new Semaphore(3);// 机器数
for (int i = 0; i < works; i++) {
new Thread(new Work(i, semaphore)).start();
}
}
}
sleep和wait区别：
wait和notify区别
wait和notify都是Object中的方法
wait和notify执行前线程都必须获得对象锁
wait的作用是使当前线程进行等待
notify的作用是通知其他等待当前线程的对象锁的线程
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