· 1. 等待多线程完成的CountDownLatch
构造函数接收一个int类型的参数作为计数器,如果想等待N个点,就传入N。当调用CountDownLatch的countDown方法时,N就会减一,直至减为零。使用await方法等待,当N的值变为零,执行await的线程继续执行。
public class CountDownTest {
static CountDownLatch c = new CountDownLatch(2);
static ExecutorService pool = Executors.newFixedThreadPool(2);
public static void main(String agrs[]){
pool.execute(new Runnable() {
public void run() {
try {
TimeUnit.MILLISECONDS.sleep(3);
}catch (InterruptedException e){
e.printStackTrace();
}
System.out.println("This is A");
c.countDown();
}
});
pool.execute(new Runnable() {
public void run() {
try {
TimeUnit.MILLISECONDS.sleep(3);
}catch (InterruptedException e){
e.printStackTrace();
}
System.out.println("This is B");
c.countDown();
}
});
try {
c.await();
}catch (InterruptedException e){
}
System.out.println("This is main");
}
}
2. 同步屏障CyclicBarrier
可循环使用的屏障。它要做的事情,让一组线程到达屏障时被阻塞,直到最后一个线程到达屏障时,屏障才会打开,所有被屏障拦截的线程才会继续运行。
默认构造方法CyclicBarrier(int parties),其参数表示屏障拦截的线程数,每个线程调用await方法告诉CyclicBarrier已经到达屏障,然后当前线程阻塞。
public class CylicBarrierTest {
static CyclicBarrier c = new CyclicBarrier(2);
static ExecutorService pool = Executors.newFixedThreadPool(2);
public static void main(String args[]){
pool.execute(new Runnable() {
public void run() {
System.out.println("this is A");
try {
c.await();
System.out.println("this is Aa");
}catch (Exception e){
e.printStackTrace();
}
}
});
pool.execute(new Runnable() {
public void run() {
System.out.println("this is B");
try {
c.await();
System.out.println("this is Bb");
}catch (Exception e){
e.printStackTrace();
}
}
});
pool.shutdown();
}
}
3. CountDownLatch vs CyclicBarrier
CountDownLatch的计数器只使用一次,而CyclicBarrier的计数器可以使用reset方法重置,重复使用
4. 控制线程并发数的信号量 Semaphore
控制有限哥线程使用资源。使用方法 Semaphore ss = new Semaphore(N), N表示最大的并发量,每个线程使用资源前调用ss.acquire()方法获取权限,使用完后调用ss.release()方法释放权限。
5. 线程间的数据交换Exchanger
它提供一个同步点,在这个同步点,两个线程可以交换彼此的数据。
public class ExchangeTest {
private static final Exchanger<String> exgr = new Exchanger<String>();
private static ExecutorService pool = Executors.newFixedThreadPool(2);
public static void main(String args[]){
pool.execute(new Runnable() {
public void run() {
String A = "银行流水A";
try {
A = exgr.exchange(A);
System.out.println("A 当前的值:" + A);
}catch (InterruptedException e){
}
}
});
pool.execute(new Runnable() {
public void run() {
String B = "银行流水B";
try {
B = exgr.exchange(B);
System.out.println("B 当前的值:" + B);
}catch (InterruptedException e){
}
}
});
pool.shutdown();
}
原文地址:https://www.cnblogs.com/labimeilexin/p/9372039.html
时间: 2024-11-10 19:34:02