Juc_no juc situation

The difference between Synchronized and Lock

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

class Ticket{
    private int number = 30;
    private Lock lock = new ReentrantLock();

    public void sale(){
        lock.lock();
        try{
            if(number > 0){
                System.out.println(Thread.currentThread().getName() + "\t卖出了" + (number--) + "还有" + number + "张");
            }
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }

    }
}
public class Demo07 {
    public static void main(String[] args) {
        Ticket ticket = new Ticket();
        new Thread(()->{for (int i = 0; i < 40; i++) ticket.sale(); },"A").start();
        new Thread(()->{for (int i = 0; i < 40; i++) ticket.sale(); },"B").start();
        new Thread(()->{for (int i = 0; i < 40; i++) ticket.sale(); },"C").start();
//        new Thread(new Runnable() {
//            @Override
//            public void run() {
//                for (int i = 0; i < 40; i++) {
//                    ticket.sale();
//                }
//            }
//        },"A").start();
//        new Thread(new Runnable() {
//            @Override
//            public void run() {
//                for (int i = 0; i < 40; i++) {
//                    ticket.sale();
//
//                }
//            }
//        },"B").start();
//        new Thread(new Runnable() {
//            @Override
//            public void run() {
//                for (int i = 0; i < 40; i++) {
//                    ticket.sale();
//
//                }
//            }
//        },"C").start();
    }
}

What is a lock and how to judge a lock

The most basic producer consumer

public class Demo09 {
    public static void main(String[] args) {
        Data data = new Data();
        new Thread(()->{for (int i = 0;i < 10;i++) {
            try {
                data.increment();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        },"A").start();
        new Thread(()->{for (int i = 0;i < 10;i++) {
            try {
                data.decrement();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        },"B").start();
    }
}
class Data{
    private int number = 0;

    public synchronized void increment() throws InterruptedException {
        if(number != 0){
            this.wait();
        }
        number ++;
        System.out.println(Thread.currentThread().getName() + "=>" + number);
        this.notifyAll();
    }
    public synchronized void decrement() throws InterruptedException {
        if(number == 0){
            this.wait();
        }
        number--;
        System.out.println(Thread.currentThread().getName() + "=>" + number);
        this.notifyAll();
    }
}

If there are more than two threads, then
if is changed to while

public class Demo09 {
    public static void main(String[] args) {
        Data data = new Data();
        new Thread(()->{for (int i = 0;i < 10;i++) {
            try {
                data.increment();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        },"A").start();
        new Thread(()->{for (int i = 0;i < 10;i++) {
        try {
            data.decrement();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    },"B").start();

        new Thread(()->{for (int i = 0;i < 10;i++) {
            try {
                data.decrement();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        },"C").start();

        new Thread(()->{for (int i = 0;i < 10;i++) {
            try {
                data.decrement();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        },"D").start();
}
}
class Data{
    private int number = 0;

    public synchronized void increment() throws InterruptedException {
        while (number != 0){
            this.wait();
        }
        number ++;
        System.out.println(Thread.currentThread().getName() + "=>" + number);
        this.notifyAll();
    }
    public synchronized void decrement() throws InterruptedException {
        while (number == 0){
            this.wait();
        }
        number--;
        System.out.println(Thread.currentThread().getName() + "=>" + number);
        this.notifyAll();
    }
}