上海Java后端開發(fā)常考面試題有哪些？

class ShareDataLock{
    // 線程執(zhí)行的條件 1：線程1執(zhí)行 2：線程2執(zhí)行 3：線程3執(zhí)行
    int number =1;
    // 鎖
    Lock lock = new ReentrantLock();
    // 從鎖中獲得3個(gè)條件變量
    Condition condition1 = lock.newCondition();
    Condition condition2 = lock.newCondition();
    Condition condition3 = lock.newCondition();

    // 第一個(gè)線程run之后執(zhí)行的方法
    public void f1(){
        lock.lock();
        try {
            // 如果條件值不為1 就掛起等待
            while(number!=1){
                condition1.await();
            }
            // 故意阻塞100毫秒，看看其他的線程會(huì)不會(huì)不再排隊(duì)
            Thread.sleep(100);
            System.out.println("------1--------");
            // 線程1 執(zhí)行完畢 把變量設(shè)置為2
            number = 2;
            // 喚醒第2個(gè)條件變量
            condition2.signal();
        } catch (Exception e) {
          e.printStackTrace();
        } finally {
            // 不管拋沒拋出異常都要解鎖，防止線程死鎖
          lock.unlock();
        }
    }
    
    public void f2(){
        lock.lock();
        try {
            while(number!=2){
                condition2.await();
            }
            System.out.println("------2--------");
            number = 3;
            condition3.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
    
    public void f3(){
        lock.lock();
        try {
            while(number!=3){
                condition3.await();
            }
            System.out.println("------3--------");
            number = 1;
            condition1.signal();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
}

public class SynchronizedAndReentrantLockDemo {

    public static void main(String[] args) {
        ShareDataLock shareDataLock = new ShareDataLock();
        for (int i = 0; i < 10; i++) {
            // 3個(gè)線程分別執(zhí)行1,2,3 3個(gè)方法 ，并且同時(shí)就緒
            new Thread(()->shareDataLock.f1(),"AA").start();
            new Thread(()->shareDataLock.f2(),"bb").start();
            new Thread(()->shareDataLock.f3(),"cc").start();
        }

    }
}