多线程练习（卖票和转账）

@Slf4j(topic = "c.ExerciseSell")
public class ExerciseSell {
    public static void main(String[] args) throws InterruptedException {
        // 模拟多人买票
        TicketWindow window = new TicketWindow(1000);

        // 所有线程的集合
        List threadList = new ArrayList();
        // 卖出的票数统计
        List amountList = new Vector();
        for (int i = 0; i  {
                // 买票
                int amount = window.sell(random(5));
                // 统计买票数
                amountList.add(amount);
            });
            threadList.add(thread);
            thread.start();
        }

        for (Thread thread : threadList) {
            thread.join();
        }

        // 统计卖出的票数和剩余票数
        log.debug("余票：{}", window.getCount());
        log.debug("卖出的票数：{}", amountList.stream().mapToInt(i -> i).sum());
    }

    // Random 为线程安全
    static Random random = new Random();

    // 随机 1~5
 服务器托管网   public static int random(int amount) {
        r服务器托管网eturn random.nextInt(amount) + 1;
    }
}

// 售票窗口
class TicketWindow {
    //此时 count是共享变量
    private int count;

    public TicketWindow(int count) {
        this.count = count;
    }

    // 获取余票数量
    public int getCount() {
        return count;
    }

    // 售票 加上synchronized 同一时刻只有一个线程可以访问此线程
    public synchronized int sell(int amount) {
        if (this.count >= amount) {
            this.count -= amount;
            return amount;
        } else {
            return 0;
        }
    }
}

22:09:36.690 c.ExerciseSell [main] - 余票：0
Exception in thread "main" java.lang.NullPointerException
	at cn.itcast.n4.exercise.ExerciseSell.lambda$main$1(ExerciseSell.java:37)
	at java.util.stream.ReferencePipeline$4$1.accept(ReferencePipeline.java:210)
	at java.util.ArrayList$ArrayListSpliterator.forEachRemaining(ArrayList.java:1384)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.IntPipeline.reduce(IntPipeline.java:457)
	at java.util.stream.IntPipeline.sum(IntPipeline.java:415)
	at cn.itcast.n4.exercise.ExerciseSell.main(ExerciseSell.java:37)

public static void main(String[] args) throws InterruptedException {
        //注意有A B两个账户
        Account a = new Account(1000);
        Account b = new Account(1000);
        Thread t1 = new Thread(() -> {
            for (int i = 0; i  {
            for (int i = 0; i = amount) {
                this.setMoney(this.getMoney() - amount);
                target.setMoney(target.getMoney() + amount);
            }
        }
    }