什么是juc

在java的java.util.concurrent包下的工具。

锁

传统的synchronize

public class SealTicket {
    int total = 50;
    public synchronized void seal() {
        if (total > 0) {
            System.out.println(Thread.currentThread().getName()
                    + "卖出第"
                    + (total--)
                    + "张，剩余：" + total
            );
        }
    }
}

JUC 的锁

public class SealTicket {
    int total = 50;
    Lock lock = new ReentrantLock();
    public void seal() {
         lock.lock();
        if (total > 0) {
            System.out.println(Thread.currentThread().getName()
                    + "卖出第"
                    + (total--)
                    + "张，剩余：" + total
            );
        }
        lock.unlock();
    }
}

Synchronize 和 Lock的区别

生产者和消费者问题

版本 synchronize

public class Data {

    int i = 0;
    public synchronized void add() throws InterruptedException {
        if (i != 0) {
            this.wait();
        }
        i++;
        System.out.println(Thread.currentThread().getName() + "=="+ i);
        this.notifyAll();
    }
    public synchronized void remove() throws InterruptedException {
        if (i == 0) {
            this.wait();
        }
        i--;
        System.out.println(Thread.currentThread().getName() + "=="+ i);
        this.notifyAll();
    }
}


public class Producer {
    public static void main(String[] args) {
        Data data = new Data();
        new Thread(() -> {
            for (int i = 0; i < 60; i++) {
                try {
                    data.add();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            }
        }, "a").start();

        new Thread(() -> {
            for (int i = 0; i < 60; i++) {
                try {
                    data.remove();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
            }
        }, "b").start();


//        new Thread(() -> {
//            for (int i = 0; i < 60; i++) {
//                sealTicket.seal();
//            }
//        }, "c").start();


    }
}

版本 Lock

8锁问题

锁是什么，锁锁的是谁？