JUC梳理
JUC包的分类
并发工具类
CountDownLatch
Demo
public class CountDownLatchDemo {
public static void main(String[] args) throws InterruptedException {
new CountDownLatchDemo().go();
}
private void go() throws InterruptedException {
CountDownLatch countDownLatch = new CountDownLatch(3);
new Thread(new Task(countDownLatch),"Thread1").start();
Thread.sleep(1000);
new Thread(new Task(countDownLatch),"Thread2").start();
Thread.sleep(1000);
new Thread(new Task(countDownLatch),"Thread3").start();
countDownLatch.await();
System.out.println("所有线程已到达，主线程开始执行"+System.currentTimeMillis());
}
class Task implements Runnable {
private CountDownLatch countDownLatch;
public Task(CountDownLatch countDownLatch) {
this.countDownLatch = countDownLatch;
}
@Override
public void run() {
System.out.println("线程"+Thread.currentThread().getName() + "已经到达"+System.currentTimeMillis());
countDownLatch.countDown();
}
}
}
运行结果
线程Thread1已经到达1599366228071
线程Thread2已经到达1599366229085
线程Thread3已经到达1599366230100
所有线程已到达，主线程开始执行1599366230101
CyclicBarrier
CyclicBarrier和CountDownLatch不同的地方在于，CountDownLatch的子线程可以在其他线程等待的状态下继续执行，而CyclicBarrier要等到所有线程都awaiting再一起执行。
Demo
public class CyclicBarrierDemo {
public static void main(String[] args) throws InterruptedException {
new CyclicBarrierDemo().go();
}
private void go() throws InterruptedException {
CyclicBarrier cyclicBarrier = new CyclicBarrier(3);
new Thread(new Task(cyclicBarrier),"Thread1").start();
Thread.sleep(1000);
new Thread(new Task(cyclicBarrier),"Thread2").start();
Thread.sleep(1000);
new Thread(new Task(cyclicBarrier),"Thread3").start();
}
class Task implements Runnable {
private CyclicBarrier cyclicBarrier;
public Task(CyclicBarrier cyclicBarrier) {
this.cyclicBarrier = cyclicBarrier;
}
@Override
public void run() {
System.out.println("线程"+Thread.currentThread().getName() + "已经到达"+System.currentTimeMillis());
try {
cyclicBarrier.await();
} catch (InterruptedException | BrokenBarrierException e) {
e.printStackTrace();
}
System.out.println("线程"+Thread.currentThread().getName() + "开始处理"+System.currentTimeMillis());
}
}
}
运行结果
线程Thread1已经到达1599367002749
线程Thread2已经到达1599367003757
线程Thread3已经到达1599367004769
线程Thread1开始处理1599367004770
线程Thread2开始处理1599367004771
线程Thread3开始处理1599367004771
Semaphore
Demo
public class SemaphoreDemo {
public static void main(String[] args) {
ThreadFactory threadFactory = new NameTreadFactory();
RejectedExecutionHandler handler = new MyIgnorePolicy();
// 线程池
BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(2);
ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(2, 50, 10,
TimeUnit.SECONDS, workQueue, threadFactory, handler);
// 只能5个线程同时访问
final Semaphore semaphore = new Semaphore(5);
for (int i = 0; i < 20; i++) {
final int NO = i;
Runnable run = new Runnable() {
@Override
public void run() {
try {
// 获取许可
semaphore.acquire();
System.out.println("Accessing: " + NO);
Thread.sleep((long) (Math.random() * 10000));
// 访问完后，释放
semaphore.release();
} catch (InterruptedException e) {
e.printStackTrace();
}
}
};
poolExecutor.execute(run);
}
// 退出线程池
poolExecutor.shutdown();
}
static class NameTreadFactory implements ThreadFactory {
private final AtomicInteger mThreadNum = new AtomicInteger(0);
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r, "my-thread-" + mThreadNum.getAndIncrement());
System.out.println(t.getName() + " has been created");
return t;
}
}
public static class MyIgnorePolicy implements RejectedExecutionHandler {
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
doLog(r, e);
}
private void doLog(Runnable r, ThreadPoolExecutor e) {
// 可做日志记录等
System.err.println(r.toString() + " rejected");
// System.out.println("completedTaskCount: " + e.getCompletedTaskCount());
}
}
}
运行结果
my-thread-0 has been created
my-thread-1 has been created
my-thread-2 has been created
my-thread-3 has been created
my-thread-4 has been created
my-thread-5 has been created
my-thread-6 has been created
my-thread-7 has been created
my-thread-8 has been created
my-thread-9 has been created
my-thread-10 has been created
my-thread-11 has been created
my-thread-12 has been created
my-thread-13 has been created
my-thread-14 has been created
my-thread-15 has been created
my-thread-16 has been created
my-thread-17 has been created
Accessing: 0
Accessing: 1
Accessing: 4
Accessing: 5
Accessing: 6
Accessing: 7
Accessing: 3
Accessing: 8
Accessing: 9
Accessing: 10
Accessing: 11
Accessing: 12
Accessing: 13
Accessing: 14
Accessing: 15
Accessing: 16
Accessing: 17
Accessing: 18
Accessing: 19
Accessing: 2
Exchanger
Demo
public class ExchangerDemo {
public static void main(String[] args) {
Exchanger<String> exchanger = new Exchanger<>();
ThreadFactory threadFactory = new NameTreadFactory();
RejectedExecutionHandler handler = new MyIgnorePolicy();
// 线程池
BlockingQueue<Runnable> workQueue = new ArrayBlockingQueue<>(2);
ThreadPoolExecutor poolExecutor = new ThreadPoolExecutor(2, 2, 10,
TimeUnit.SECONDS, workQueue, threadFactory, handler);
poolExecutor.execute(() ->{
try {
// 女生对男生说的话
String girl = exchanger.exchange("我其实暗恋你很久了......");
System.out.println("女生说: "+girl);
} catch (InterruptedException e) {
e.printStackTrace();
}
});
poolExecutor.execute(() ->{
try {
System.out.println("女生慢慢从教室走出来.......");
TimeUnit.SECONDS.sleep(3);
// 男生对女生说的话
String boy = exchanger.exchange("我很喜欢你......");
System.out.println("男生说: "+boy);
} catch (InterruptedException e) {
e.printStackTrace();
}
});
}
static class NameTreadFactory implements ThreadFactory {
private final AtomicInteger mThreadNum = new AtomicInteger(0);
@Override
public Thread newThread(Runnable r) {
Thread t = new Thread(r, "my-thread-" + mThreadNum.getAndIncrement());
System.out.println(t.getName() + " has been created");
return t;
}
}
public static class MyIgnorePolicy implements RejectedExecutionHandler {
@Override
public void rejectedExecution(Runnable r, ThreadPoolExecutor e) {
doLog(r, e);
}
private void doLog(Runnable r, ThreadPoolExecutor e) {
// 可做日志记录等
System.err.println(r.toString() + " rejected");
// System.out.println("completedTaskCount: " + e.getCompletedTaskCount());
}
}
}
运行结果
my-thread-0 has been created
my-thread-1 has been created
女生慢慢从教室走出来.......
男生说: 我其实暗恋你很久了......
女生说: 我很喜欢你......
BlockingQueue
