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Java多线程

时间:2020-05-01 20:31:23      阅读:67      评论:0      收藏:0      [点我收藏+]

标签:priority   int   兔子   结果   回收   target   顺序   生产者   lambda表达式   

多线程

创建线程方式1

/**
 * 创建线程方式1:
 * 1、继承Thread类
 * 2、重写run方法
 * 3、调用start开启线程
 * 注意:线程开启不一定执行,由CPU调度
  */
public class ThreadTest extends Thread{
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            System.out.println("我在看代码==" + i);
        }
    }
?
    public static void main(String[] args) {
        //创建线程对象
        ThreadTest threadTest = new ThreadTest();
        //调用start方法开启线程
        threadTest.start();
            //主线程
            for (int i = 0; i < 20; i++) {
                System.out.println("我在学习多线程--" + i);
            }
    }
}

创建线程方式2

/**
 * 创建线程方式2:
 * 1、实现Runnable接口,重写run方法
 * 2、执行线程需要丢入runnable接口实现类,调用start方法
 * */
public class ThreadTest1 implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            System.out.println("我在看代码==" + i);
        }
    }
?
    public static void main(String[] args) {
        //创建runnable接口实现类的对象
        ThreadTest1 threadTest1 = new ThreadTest1();
        //创建线程对象,通过线程对象来开启线程,代理
        Thread thead = new Thread(threadTest1);
        //调用start方法开启线程
        thead.start();
        //主线程
        for (int i = 0; i < 20; i++) {
            System.out.println("我在学习多线程--" + i);
        }
    }
}

龟兔赛跑

public class Race implements Runnable{
    public static String winner;
    @Override
    public void run() {
        for (int i = 0; i <= 100; i++) {
            if("兔子".equals(Thread.currentThread().getName()) && i%10 == 0){
                try {
                    Thread.sleep(10);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            if(isOver(i)){
                break;
            }
            System.out.println(Thread.currentThread().getName() + ": 跑了" + i + "步");
        }
    }
?
    public boolean isOver(int steps){
        if(winner != null){
            return true;
        }else if(steps >= 100){
            winner = Thread.currentThread().getName();
            System.out.println("胜利者是:" + winner);
            return true;
        }else{
            return false;
        }
    }
?
    public static void main(String[] args) {
        Race race = new Race();
        new Thread(race,"乌龟").start();
        new Thread(race,"兔子").start();
?
    }
}

创建线程方式3

/**
 * 线程创建方式3:
 *
 */
public class ThreadTest2 implements Callable {
    @Override
    public Object call() throws Exception {
        for (int i = 0; i < 20; i++) {
            System.out.println(Thread.currentThread().getName() + " : 我在看代码==" + i);
        }
        return true;
    }
?
    public static void main(String[] args) throws Exception{
        ThreadTest2 t1 = new ThreadTest2();
        ThreadTest2 t2 = new ThreadTest2();
        //创建执行服务
        ExecutorService ser = Executors.newFixedThreadPool(2);
        //提交执行
        Future s1 = ser.submit(t1);
        Future s2 = ser.submit(t2);
?
        //获取结果
        Object res1 = s1.get();
        Object res2 = s2.get();
?
        //关闭服务
        ser.shutdown();
?
    }
}

静态代理

/***
 * 静态代理模式:
 * 1、真实对象和代理对象实现同一个接口
 * 2、代理对象代理真实角色
 */
public class StaticProxy {
    public static void main(String[] args) {
        new Thread().start();
        Person p = new Person("小明");
        WeddingCompany wc = new WeddingCompany(p);
        wc.happyMarry();
    }
}
?
interface Marry{
    void happyMarry();
}
?
class Person implements Marry{
    String name;
?
    public Person(String name) {
        this.name = name;
    }
?
    @Override
    public void happyMarry() {
        System.out.println(name + "结婚了!");
    }
}
?
//代理角色
class WeddingCompany implements Marry{
    private Marry target;
?
    public WeddingCompany(Marry target) {
        this.target = target;
    }
?
    @Override
    public void happyMarry() {
        before();
        this.target.happyMarry();
        after();
    }
?
    private void before(){
        System.out.println("结婚之前布置现场!");
    }
?
    private void after(){
        System.out.println("结婚之后收取费用!");
    }
}

lambda表达式

函数式接口:

  • 任何接口,如果只包含唯一一个抽象方法,那么它就是一个函数式接口

  • 对于函数式接口,可以通过lambda表达式创建该接口的对象

public class LambdaTest {
    //静态内部类
    static class Like2 implements ILike{
?
        @Override
        public void lambda() {
            System.out.println("I like java,too!");
        }
    }
    public static void main(String[] args) {
        ILike like = new Like();
        like.lambda();
        //2、静态内部类
        like = new Like2();
        like.lambda();
?
        //3、局部内部类
        class Like3 implements ILike{
?
            @Override
            public void lambda() {
                System.out.println("I like java,too too!");
            }
        }
        like = new Like3();
        like.lambda();
?
        //4、匿名内部类,没有名称,必须借助接口或者父类
        like = new ILike() {
            @Override
            public void lambda() {
                System.out.println("I like java,too too too!");
            }
        };
        like.lambda();
?
        //5、lambda简化
        like = ()->{
            System.out.println("I like java,too too too too!");
        };
        like.lambda();
?
    }
}
?
//定义一个函数式接口
interface ILike{
    void lambda();
}
?
//1、实现类
class Like implements ILike{
    @Override
    public void lambda() {
        System.out.println("I like java");
    }
}

带参数的简化

技术图片

线程状态

技术图片

sleep():线程休眠

yiled():线程礼让,不一定成功

join():线程强制执行,插队

getPriority():获取优先级(1~10)

setPriority(): 设置优先级

线程分为用户线程和守护线程

虚拟机必须确保用户线程执行完毕,不用等待守护线程(如垃圾回收、监控内存)执行完毕

setDaemon(true):设置为守护线程

线程同步

买票问题:synchronized 

synchronized

public class UnsafeBuyTicket {
    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();
        new Thread(station,"小明").start();
        new Thread(station,"小红").start();
        new Thread(station,"小华").start();
    }
?
}
?
class BuyTicket implements Runnable{
    private int ticketNum = 10;
    boolean flag = true;
    @Override
    public void run() {
        while (flag){
            buy();
        }
    }
    //默认锁的是this
    private synchronized void buy(){
        if(ticketNum <= 0){
            flag = false;
            return;
        }
        //模拟延时
        try {
            Thread.sleep(100);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(Thread.currentThread().getName() + "买到" + ticketNum--);
    }
}

Lock

public class UnsafeBuyTicket {
    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();
        new Thread(station,"小明").start();
        new Thread(station,"小红").start();
        new Thread(station,"小华").start();
    }
?
}
?
class BuyTicket implements Runnable{
    private int ticketNum = 10;
    boolean flag = true;
    private final Lock lock = new ReentrantLock();
    @Override
    public void run() {
        while (flag){
            buy();
        }
    }
?
    private void buy(){
        try {
            lock.lock();
            if(ticketNum <= 0){
                flag = false;
                return;
            }
            //模拟延时
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "买到" + ticketNum--);
        }finally {
            lock.unlock();
        }
?
    }
}

队列+锁

synchronized 和 Lock对比

  • Lock是显式锁(手动开启和关闭锁),synchronized是隐式锁,出了作用域自动释放

  • Lock只有代码块锁,synchronized有代码块锁和方法锁

  • Lock锁,JVM将花费较少的时间来调度线程,性能更好,并且具有更好的扩展性

  • 顺序:Lock>同步代码块>同步方法

线程通信

wait(): 线程一直等待,直到其它线程通知,与sleep()不同,会释放锁

notify(): 唤醒一个处于等待状态的线程

notifyAll():唤醒同一个对象上所有调用wait()方法是线程,优先级别高的线程优先调度

以上方法只能在同步方法或同步代码块中使用

生产者消费者问题:

//利用缓冲区解决:管程法
public class TestPC {
    public static void main(String[] args) {
        Container container = new Container();
        new Producer(container).start();
        new Consumer(container).start();
    }
}
?
//生产者
class Producer extends Thread{
    Container container;
    public Producer(Container container){
        this.container = container;
    }
?
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            container.push(new Chicken(i));
            System.out.println("生产了" + i + "只鸡");
        }
    }
}
?
//消费者
class Consumer extends Thread{
    Container container;
    public Consumer(Container container){
        this.container = container;
    }
?
    @Override
    public void run() {
        for (int i = 0; i < 100; i++) {
            System.out.println("消费了" + container.pop().id + "只鸡");
        }
    }
}
?
//产品
class Chicken{
    int id;//产品编号
?
    public Chicken(int id) {
        this.id = id;
    }
}
?
//缓冲区
class Container{
    //容器大小
    Chicken[] chickens = new Chicken[10];
    //容器计数器
    int count = 0;
?
    //生产者放入产品
    public synchronized void push(Chicken chicken){
        //容器满了,需要等待消费
        if(count == chickens.length){
            //等待消费,生产者等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        //未满,放入产品
        chickens[count++] = chicken;
        //通知消费者消费
        this.notifyAll();
    }
?
    //消费者消费产品
    public synchronized Chicken pop(){
        if(count == 0){
            //等待生产,消费者等待
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        count--;
        Chicken chicken = chickens[count];
        //通知生产者生产
        this.notifyAll();
        return chicken;
    }
}

 

//信号灯法
public class TestPC2 {
    public static void main(String[] args) {
        TV tv = new TV();
        new Player(tv).start();
        new Watcher(tv).start();
    }
}
//生产者-演员
class Player extends Thread{
    TV tv;
    public Player(TV tv){
        this.tv = tv;
    }
?
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            if(i%2 == 0){
                this.tv.play("快乐大本营");
            }else{
                this.tv.play("向往的生活");
            }
        }
    }
}
//消费者-观众
class Watcher extends Thread{
    TV tv;
    public Watcher(TV tv){
        this.tv = tv;
    }
?
    @Override
    public void run() {
        for (int i = 0; i < 20; i++) {
            tv.watch();
        }
    }
}
//产品-节目
class TV{
    //演员表演,观众等待 T
    //观众观看,演员等待 F
    String show;//节目
    boolean flag = true;
    public synchronized void play(String show){
        if(!flag){
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("演员表演了" + show );
        //通知观众观看
        this.notifyAll();
        this.show = show;
        this.flag = !this.flag;
    }
?
    public synchronized void watch(){
        if(flag){
            try {
                this.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
        System.out.println("观众观看了" + show );
        //通知演员表演
        this.notifyAll();
        this.flag = !this.flag;
    }
}
 

Java多线程

标签:priority   int   兔子   结果   回收   target   顺序   生产者   lambda表达式   

原文地址:https://www.cnblogs.com/come-on-pxw/p/12814376.html

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