以下代码无法正常工作：
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
class Worker implements Runnable {
public void run() {
System.out.println("Started.");
process();
}
private Random random = new Random();
private Object lock1 = new Object();
private Object lock2 = new Object();
private static List<Integer> list1 = new ArrayList<Integer>();
private static List<Integer> list2 = new ArrayList<Integer>();
public void stageOne() {
synchronized (lock1) {
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
list1.add(random.nextInt(100));
}
}
public void stageTwo() {
synchronized (lock2) {
try {
Thread.sleep(1);
} catch (InterruptedException e) {
e.printStackTrace();
}
list2.add(random.nextInt(100));
}
}
public void process() {
for(int i=0; i<1000; i++) {
stageOne();
stageTwo();
}
}
public static void show() {
System.out.println("List1: " + list1.size());
System.out.println("List2: " + list2.size());
}
}
public class JavaTest {
public static void main(String[] args) {
long start = System.currentTimeMillis();
Thread t1 = new Thread(new Worker());
t1.start();
Thread t2 = new Thread(new Worker());
t2.start();
try {
t1.join();
t2.join();
} catch (InterruptedException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Completed.");
long end = System.currentTimeMillis();
System.out.println("Time taken: " + (end - start));
Worker.show();
}
}
@H_404_4@当我运行这个程序时,我希望list1和list2每个包含2000个项目,并且程序需要大约2000毫秒.然而,很多时候我得到的列表少于2000个项目,尽管它确实在2000毫秒左右完成.有时我甚至会得到一个ArrayOutOfBounds异常
Started.
Started.
Exception in thread "Thread-1" java.lang.ArrayIndexOutOfBoundsException: 163
at java.util.ArrayList.add(ArrayList.java:459)
at Worker.stageOne(JavaTest.java:34)
at Worker.process(JavaTest.java:53)
at Worker.run(JavaTest.java:14)
at java.lang.Thread.run(Thread.java:748)
Completed.
Time taken: 2217
List1: 1081
List2: 1079
@H_404_4@我希望stageOne和stageTwo中的每个锁都应该阻止线程相互干扰.但事实似乎并非如此.这段代码有什么问题？
解决方法
您的锁定对象不是静态的,因此每个线程在不同的监视器上进行同步.所以锁没有任何影响.
