使用场景:
一个或N个线程,等待其它线程完成某项操作之后才能继续往下执行。CountDownLatch描述的是,一个或N个线程等待其他线程的关系。
使用方法:
- 设CountDownLatch个数:CountDownLatch countDownLatch=new CountDownLatch(3);
- 在等待线程中await:countDownLatch.await();
- 在其他线程中减少count值:countDownLatch.getCount();
- 一旦其他线程中的countDownLatch.getCount()的次数为实例化时的count值,就唤醒等待线程
public class T06_TestCountDownLatch {
public static void main(String[] args) {
usingJoin();
usingCountDownLatch();
} private static void usingCountDownLatch() {
Thread[] threads = new Thread[100];
CountDownLatch latch = new CountDownLatch(threads.length); for(int i=0; i<threads.length; i++) {
threads[i] = new Thread(()->{
int result = 0;
for(int j=0; j<10000; j++) result += j;
latch.countDown();
});
} for (int i = 0; i < threads.length; i++) {
threads[i].start();
} try {
latch.await();
} catch (InterruptedException e) {
e.printStackTrace();
} System.out.println("end latch");
} private static void usingJoin() {
Thread[] threads = new Thread[100]; for(int i=0; i<threads.length; i++) {
threads[i] = new Thread(()->{
int result = 0;
for(int j=0; j<10000; j++) result += j;
});
} for (int i = 0; i < threads.length; i++) {
threads[i].start();
} for (int i = 0; i < threads.length; i++) {
try {
threads[i].join();
} catch (InterruptedException e) {
e.printStackTrace();
}
} System.out.println("end join");
}
}