lock&synchronized

1，synchronized是内置的Java关键字；Lock是一个Java类
2，synchronized无法判断获取锁的状态；Lock可以判断
3，synchronized会自动释放锁；Lock必须要手动加锁和释放锁（可能会遇到死锁）
4，synchronized：线程1（获得锁->阻塞）、线程2（等待）；Lock不一定会一直等待下去，Lock会有一个trylock去尝试获取锁，不会造成长久的等待
5，synchronized是可重入锁，不可以中断的，非公平的；Lock，可重入的，可以判断锁，可以自己设置公平锁和非公平锁
6，synchronized适合锁少量的代码同步问题；Lock适合锁大量的同步代码

卖票例子

1，synchronized

/**
 * 真正的多线程开发
 * 线程就是一个单独的资源类，没有任何的附属操作！
 */
public class SaleTicketDemo01 {
    public static void main(String[] args) {
        //多线程操作
        //并发：多线程操作同一个资源类，把资源类丢入线程
        Ticket ticket = new Ticket();

        //@FunctionalInterface 函数式接口 jdk1.8之后 lambda表达式
        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();
    }
}
//资源类
//属性+方法
//oop
class Ticket{
    private int number=50;


    //卖票的方式
    // synchronized 本质：队列，锁
    public synchronized void sale(){
        if(number>0){
            System.out.println(Thread.currentThread().getName()+" 卖出了第"+number+" 张票,剩余："+number+" 张票");
            number--;
        }
    }
}

2，lock

public class SaleTicketDemo02 {
    public static void main(String[] args) {
        //多线程操作
        //并发：多线程操作同一个资源类，把资源类丢入线程
        Ticket2 ticket = new Ticket2();
        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();
    }
}

//lock三部曲
//1、    Lock lock=new ReentrantLock();
//2、    lock.lock() 加锁
//3、    finally=> 解锁：lock.unlock();
class Ticket2{
    private int number=50;

    Lock lock=new ReentrantLock();

    //卖票的方式
    // 使用Lock 锁
    public void sale(){
        //加锁
        lock.lock();
        try {
            //业务代码
            if(number>=0){
                System.out.println(Thread.currentThread().getName()+" 卖出了第"+number+" 张票,剩余："+number+" 张票");
                number--;
            }
        }catch (Exception e) {
            e.printStackTrace();
        }
        finally {
            //解锁
            lock.unlock();
        }
    }
}

等待唤醒机制

多个线程交替打印1，0

1，synchronized

package com.llb.juc.producerAndCunsumer;

class Data{
    private int number = 0;

    //+1
    public synchronized void increment() throws InterruptedException {
        //使用while防止虚假唤醒
        while (number!=0){
            this.wait();
        }
        number++;
        System.out.println(Thread.currentThread().getName()+" number : "+number);
        this.notifyAll();
    }

    //-1
    public synchronized void decrement() throws InterruptedException {
        while (number != 1){
            this.wait();
        }
        number --;
        System.out.println(Thread.currentThread().getName()+" number : "+number);
        this.notifyAll();
    }
}
public class DemoSynchronized {
    public static void main(String[] args) {
        Data data = new Data();
        new Thread(()->{
            try {
                for (int i = 0; i < 5; i++) {
                    data.increment();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "AA").start();
        new Thread(()->{
            try {
                for (int i = 0; i < 5; i++) {
                    data.decrement();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "BB").start();
        new Thread(()->{
            try {
                for (int i = 0; i < 5; i++) {
                    data.increment();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "CC").start();
        new Thread(()->{
            try {
                for (int i = 0; i < 5; i++) {
                    data.decrement();
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }, "DD").start();
    }
}

2，lock

package com.llb.juc.producerAndCunsumer;

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

class Data2{
    private int number = 0;
    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();

    //+1
    public void increment(){
        lock.lock();
        try {
            //使用while防止虚假唤醒
            while (number!=0){
                condition.await();
            }
            number++;
            System.out.println(Thread.currentThread().getName()+" number : "+number);
            condition.signalAll();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }

    //-1
    public void decrement(){
        lock.lock();
        try {
            //使用while防止虚假唤醒
            while (number!=1){
                condition.await();
            }
            number--;
            System.out.println(Thread.currentThread().getName()+" number : "+number);
            condition.signalAll();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
}
public class DemoLock {
    public static void main(String[] args) {
        Data2 data2 = new Data2();
        new Thread(()->{
                for (int i = 0; i < 5; i++) {
                    data2.increment();
                }
        }, "AA").start();
        new Thread(()->{
                for (int i = 0; i < 5; i++) {
                    data2.decrement();
                }
        }, "BB").start();
        new Thread(()->{
                for (int i = 0; i < 5; i++) {
                    data2.increment();
                }
        }, "CC").start();
        new Thread(()->{
                for (int i = 0; i < 5; i++) {
                    data2.decrement();
                }
        }, "DD").start();
    }
}

精确唤醒指定线程用Condition

package com.llb.juc.producerAndCunsumer;

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

class Data3{
    Lock lock = new ReentrantLock();
    Condition c1 = lock.newCondition();
    Condition c2 = lock.newCondition();
    Condition c3 = lock.newCondition();

    private int number = 0;
    private int num = 1;
//    private String sign = "A";

    public void printA(){
        lock.lock();
        try {
            while (num!=1){
                c1.await();
            }
            System.out.println(Thread.currentThread().getName()+" : A : "+number);
            number++;
            num=2;
            c2.signal();
        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
    public void printB(){
        lock.lock();
        try {
            while (num!=2){
                c2.await();
            }
            System.out.println(Thread.currentThread().getName()+" : B : "+number);
            number++;
            num=3;
            c3.signal();
        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
    public void printC(){
        lock.lock();
        try {
            while (num!=3){
                c3.await();
            }
            System.out.println(Thread.currentThread().getName()+" : C : "+number);
            number++;
            num=1;
            c1.signal();
        }catch (Exception e) {
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
}
public class DemoCondition {
    public static void main(String[] args) {
        Data3 data3 = new Data3();
        new Thread(()->{
            for (int i = 0; i < 5; i++) {
                data3.printA();
            }
        }, "AA").start();
        new Thread(()->{
            for (int i = 0; i < 5; i++) {
                data3.printB();
            }
        }, "BB").start();
        new Thread(()->{
            for (int i = 0; i < 5; i++) {
                data3.printC();
            }
        }, "CC").start();
    }
}