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1.如何让两个线程嫩能够交叉执行
要让线程能够交叉执行,需要用到锁。看如下代码:
package Test;/**
/**
* @author Administrator wangtao
* @createdate 2017-10-10
*/
public class demo3 {
public static void main(String[] args ){
Object lock = new Object();
Thread thread1 = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lock){
System.out.println("A 1");
try {
lock.wait();
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println("A 2");
System.out.println("A 3");
}
}
});
Thread thread2 = new Thread(new Runnable() {
@Override
public void run() {
synchronized (lock){
System.out.println("B 1");
System.out.println("B 2");
System.out.println("B 3");
lock.notify();
}
}
});
thread1.start();
thread2.start();
}
}
线程1先获得锁,执行一段任务之后,调用wait()方法,让线程释放锁,线程2获得锁,执行任务。等到线程2执行完成后,通过notify()。唤醒线程。
2.四个线程 A B C D,其中 D 要等到 A B C 全执行完毕后才执行,而且 A B C 是同步运行的
1.创建一个计数器,设置初始值,CountdownLatch countDownLatch = new CountDownLatch(2);
2.在 等待线程 里调用 countDownLatch.await() 方法,进入等待状态,直到计数值变成 0;
3.在 其他线程 里,调用 countDownLatch.countDown() 方法,该方法会将计数值减小 1;
4.当 其他线程 的 countDown() 方法把计数值变成 0 时,等待线程 里的 countDownLatch.await() 立即退出,继续执行下面的代码。
package Test;/**
import java.util.concurrent.CountDownLatch;
/**
* @author Administrator wangtao
* @createdate 2017-10-10
*/
public class demo4 {
public static void main(String[] args){
int worker =3;
CountDownLatch countDownLatch = new CountDownLatch(worker);
new Thread(new Runnable() {
@Override
public void run() {
System.out.println("D is waiting for other three threads");
try {
countDownLatch.await();//线程处于等待状态,直到计数器等于0线程会继续执行
System.out.println("All done, D starts working");
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start();
for(char threadName='A';threadName <= 'C';threadName++){
final String tN = String.valueOf(threadName);
new Thread(new Runnable() {
@Override
public void run() {
System.out.println(tN + "is working");
try {
Thread.sleep(100);
} catch (InterruptedException e) {
e.printStackTrace();
}
System.out.println(tN +"finished");
countDownLatch.countDown();
}
}).start();
}
}
}