竞态条件

/**
 * 竞态条件——结果和执行时序有关，可能正确也可能不正确
 */
public class CounterThread extends Thread{
    private static int counter = 0;
    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            counter++;  // 非原子操作
        }
    }

    public static void main(String[] args) throws InterruptedException {
        int num = 1000;
        Thread[] threads = new Thread[num];
        for (int i = 0; i < num; i++) {
            threads[i] = new CounterThread();
            threads[i].start();
        }
        for (int i = 0; i < num; i++) {
            threads[i].join();
        }
        System.out.println(counter);
    }

    /**
     * 999935
     */
}