java中证明++操作是非原子的

来源：互联网发布：手机淘宝如何改店名编辑：程序博客网时间：2024/05/18 00:29

class SerialNumberGenerator{private static volatile int i=0;//不是同步的，多个线程操作可能会冲突public static int nextSerialNumber(){return i++;}}class CircularSet{private int[] array;private int len;private int index=0;public CircularSet(int size){this.len=size;array=new int[len];for(int i=0;i<len;i++){array[i]=-1;}}public synchronized void add(int n){array[index]=n;index=++index%len;}public synchronized boolean contains(int n){for(int i=0;i<len;i++){if(array[i]==n){return true;}}return false;}}public class Test {private static final int SIZE=100;private static CircularSet mCircularSet=new CircularSet(1000);private static ExecutorService mExecutorService=Executors.newCachedThreadPool();public static void main(String[] args) throws InterruptedException {for(int i=0;i<SIZE;i++){mExecutorService.execute(new SerialChecker());}TimeUnit.SECONDS.sleep(5);}static class SerialChecker implements Runnable{@Overridepublic void run() {while(true){int serial=SerialNumberGenerator.nextSerialNumber();if(mCircularSet.contains(serial)){System.out.println("Duplicate:"+serial);System.exit(0);}mCircularSet.add(serial);}}}}

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