java-多线程

重点：线程实现、线程同步

新生–>就绪–>阻塞–>运行–>死亡–>

//创建线程方法一：继承THread类，重写run（）方法，调用start方法开启线程

//总结：注意，线程开启不一定立即执行，有cpu调度执行

public class Text extends Thread{
    @Override
    public void run() {
        //run方法线程体
        for (int i = 0; i < 20; i++) {
            System.out.println("我在看代码----");
        }
    }

    public static void main(String[] args) {
        //main线程， 主线程

        //创建线程对象
        Text text = new Text();
        //开启线程start是交替执行
        text.start();

        for (int i = 0; i < 20; i++) {
            System.out.println("我早");
        }
    }
}

//下载图片案例

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.io.IOException;
import java.net.URL;

//练习Thread ， 实现多线程下载图片
public class TestThread2 extends Thread{

    private String url;//保存图片地址
    private String name;//保存的文件名

    public TestThread2(String url, String name){
        this.url = url;
        this.name = name;
    }

    //下载图片线程的执行体
    @Override
    public void run() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(url, name);
        System.out.println("下载了文件名："+name);
    }

    public static void main(String[] args){
        TestThread2 t1 = new TestThread2("https://img-blog.csdnimg.cn/20200305081800551.jpg", "1.jpg");
        TestThread2 t2 = new TestThread2("https://img-blog.csdnimg.cn/20200305082009840.jpg", "2.jpg");
        t1.start();
        t2.start();
    }
}

//下载器
class WebDownloader{
    //下载方法
    public void downloader(String url, String name){
        try {
            FileUtils.copyURLToFile(new URL(url), new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("IO异常");
        }

    }
}

//创建线程方法2 ； 实现runnable接口，重写run方法， 执行线程需要丢入runnable接口实现类，调用start方法
public class TextThread3 implements Runnable{

    @Override
    public void run() {
        for (int i = 0; i < 1000; i++) {
            System.out.println("下载了文件名：");
        }
    }

    public static void main(String[] args){
        //创建runnable接口的实现类对象
        TextThread3 thread = new TextThread3();
        //创建线程对象，通过线程对象来开启我们的线程，代理
        new Thread(thread).start();

        for (int i = 0; i < 1000; i++) {
            System.out.println("我在学习----");
        }
    }
}

//多线程同时操作同一个对象
//买火车票的例子

//发现问题：多个线程操作同一个资源的情况下，线程不安全，数据紊乱，
public class TestThread4 implements Runnable{

    //票数
    int ticketNum = 10;

    @Override
    public void run() {
        while(true){
            if (ticketNum<=0){
                break;
            }
            //模拟延时
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName()+"-->拿到了"+ticketNum--+"票");

        }
    }

    public static void main(String[] args) {
        TestThread4 ticket = new TestThread4();


        new Thread(ticket, "小明").start();
        new Thread(ticket, "老师").start();
        new Thread(ticket, "夯牛").start();
    }
}

//模拟龟兔赛跑

public class Race implements Runnable {

    //胜利者
    private  static String winner;
    @Override
    public void run() {
        for (int i = 0; i <= 100; i++) {

            //模拟兔子睡觉
            if (Thread.currentThread().getName().equals("兔子")&&i%10==0){
                try {
                    Thread.sleep(1);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }

            //判断比赛是否结束
            boolean flag = gameOver(i);
            //如果比赛结束停止程序
            if (flag){
                break;
            }
            System.out.println(Thread.currentThread().getName()+"-->跑了"+i+"米");

        }
    }
    //判断是否完成比赛
    private boolean gameOver(int steps){
        //判断是否有胜利者
        if (winner!=null){ //已经有了胜利者
            return true;
        }{
            if (steps>=100){
                winner = Thread.currentThread().getName();
                System.out.println("winner is"+winner);
                return true;
            }
        }
        return false;
    }

    public static void main(String[] args) {
        Race race = new Race();

        new Thread(race,"兔子").start();
        new Thread(race,"乌龟").start();
    }
}

public class TestCallable implements Callable {

    private String url;//保存图片地址
    private String name;//保存的文件名

    public TestCallable(String url, String name){
        this.url = url;
        this.name = name;
    }

    //下载图片线程的执行体
    @Override
    public Boolean call() {
        WebDownloader webDownloader = new WebDownloader();
        webDownloader.downloader(url, name);
        System.out.println("下载了文件名："+name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException{
        TestCallable t1 = new TestCallable("https://img-blog.csdnimg.cn/20200305081800551.jpg", "1.jpg");
        TestCallable t2 = new TestCallable("https://img-blog.csdnimg.cn/20200305082009840.jpg", "2.jpg");
        //创建执行服务：
        ExecutorService ser = Executors.newFixedThreadPool(2);
        //提交执行
        Future result1 = ser.submit(t1);
        Future result2 = ser.submit(t2);

        //获取结果
        boolean rs1 = result1.get();
        boolean rs2 = result2.get();

        //关闭服务
        ser.shutdownNow();
    }
}

class WebDownloader{
    //下载方法
    public void downloader(String url, String name){
        try {
            FileUtils.copyURLToFile(new URL(url), new File(name));
        } catch (IOException e) {
            e.printStackTrace();
            System.out.println("IO异常");
        }

    }
}

//代理是线程底部实现原理

//静态代理模式总结：
//真实对象和代理对象都要实现同一个接口
//代理对象必须代理真实
//好处：
//代理对象可以做很多真实对象做不了的事情
//真实对象可以专注自己的事情
public class StacticProxy {
    public static void main(String[] args) {
        You you = new You();//你要结婚
        WweddingCompany wenddingCompany = new WweddingCompany(new You());
        wenddingCompany.HappyMarry();
    }
}

interface Marry{ //接口
    void HappyMarry();
}

//真实角色，你去结婚
class You implements Marry{
    @Override
    public void HappyMarry() {
        System.out.println("我结婚了");
    }
}

//代理角色， 帮助你结婚
class WweddingCompany implements Marry{
    //代理-->真实目标角色
    private Marry target;
    public WweddingCompany(Marry target){
        this.target = target;
    }
    @Override
    public void HappyMarry() {
        before();
        this.target.HappyMarry();//这就是真实对象。
        after();
    }
    private void after() {
        System.out.println("结婚后，收尾款");
    }
    private void before() {
        System.out.println("接获前，不知香肠");
    }
}

函数式编程

public class lamda1 {
    public static void main(String[] args) {
        ILike love = null;
        System.out.println("得不到");
        love = a -> System.out.println("i love wei" + a);
        love.lamda(520);
    }
}
//1、定义一个函数式接口、
interface ILike{
    void lamda(int a);
}
//总结：
    // lambda表达式只能有一行代码才能不用花括号
    //前提：接口只能是函数式接口，接口中只能由一个方法
    //多个参数也可以去掉参数类型，要去掉都去掉。但是必须加括号
    //

//测试stop
//1、建议线程正常停止--->利用次数，不建议死循环
//2、建议使用标志位--->设置一个标志位
//3、不要使用stop或者destroy等过时或者JDK不建议使用的方法
public class test_stop implements Runnable{

    //1、设置一个标志位
    private boolean flag = true;
    @Override
    public void run() {
        int i = 0;
        while(flag){
            System.out.println("runrun"+i++);
        }
    }
    //2、设置一个公开的方法停止线程，转换标志位
    public void stop(){
        this.flag = false;
    }

    public static void main(String[] args) {
        test_stop testStop = new test_stop();
        new Thread(testStop).start();
        for (int i = 0; i < 1000; i++) {
            System.out.println("main"+i);
            if(i==900){
                //调用标志位让线程停止
                testStop.stop();
                System.out.println("线程停止了");
            }
        }

    }
}


//模拟倒计时。。。
public class TestSleep {

    public static void main(String[] args) {
        //打印当前系统时间
        Date startTime = new Date(System.currentTimeMillis());//获取系统当前时间
        while(true){
            try {
                Thread.sleep(1000);
                System.out.println(new SimpleDateFormat("HH:mm:ss").format(startTime));
                startTime = new Date(System.currentTimeMillis());//更新当前时间
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    //模拟倒计时
    public static void tenDown() throws InterruptedException {
        int num = 10;

        while(true) {
            Thread.sleep(1000);
            System.out.println(num--);
            if (num<=0){
                break;
            }
        }
    }
}

//线程礼让
//礼让比一定成功，看CPU心情

//测试join方法//想象插队
public class TestJion implements Runnable {

    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            System.out.println("vip来了");
        }
    }
    public static void main(String[] args) throws InterruptedException {
        //启动线程
        TestJion testJion = new TestJion();
        Thread thread = new Thread(testJion);
        //主线程
        for (int i = 0; i < 100; i++) {
            if (i == 20){
                thread.start();
                thread.join();
            }
            System.out.println("main"+i);
        }
    }
}

//观察测试线程状态
public class Teststate {

    public static void main(String[] args) throws InterruptedException {
        Thread thread = new Thread(()->{
            for (int i = 0; i < 5; i++) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
            System.out.println("");
        });

        //观察状态
        Thread.State state = thread.getState();
        System.out.println(state);
        //观察自动后
        thread.start();
        state = thread.getState();
        System.out.println(state);//Run

        while(state != Thread.State.TERMINATED){//只要线程不终止就一直输出状态
            Thread.sleep(100);
            state = thread.getState();//更新线程状态
            System.out.println(state);//输出状态
        }
    }
}

线程只能启动一次，死亡之后就不能在启动了

//测试线程的优先级
public class TestPriority {

    public static void main(String[] args) {
        //主线程默认优先级
        System.out.println(Thread.currentThread().getName()+"-->"+Thread.currentThread().getPriority());

        MyPriority myPriority = new MyPriority();
        Thread t1 = new Thread(myPriority);
        Thread t2 = new Thread(myPriority);
        Thread t3 = new Thread(myPriority);
        Thread t4 = new Thread(myPriority);
        Thread t5 = new Thread(myPriority);
        Thread t6 = new Thread(myPriority);

        //先设置优先级在启动
        t1.start();
        t2.setPriority(4);
        t2.start();
        t3.setPriority(10);
        t3.start();
        t4.setPriority(1);
        t4.start();

    }
}
class MyPriority implements Runnable{

    @Override
    public void run() {
        System.out.println(Thread.currentThread()+"-->"+Thread.currentThread().getPriority());
    }
}

//测试守护线程
//上帝守护你
public class TestDsemon {

    public static void main(String[] args) {
        God god = new God();
        You you = new You();

        Thread thread = new Thread(god);
        thread.setDaemon(true); //默认是false表示用户线程，正常的用户线程都是用户线程

        thread.start();//上帝守护线程启动
        new Thread(you).start();//用户线程启动
    }
}

//上帝
class God implements Runnable{
    @Override
    public void run() {
        while (true){
            System.out.println("上帝保佑你");
        }
    }
}
//你
class You implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 36500; i++) {
            System.out.println("你一生都很开心的活着");
        }
        System.out.println("goodbye!world");
    }

机制锁 synchronized

//不安全的买票
public class UnsafeBuyTicket {
    public static void main(String[] args) {
        BuyTicket station = new BuyTicket();

        new Thread(station, "苦逼的我").start();
        new Thread(station, "苦逼的你们").start();
        new Thread(station, "可恶的黄牛").start();
    }

}
class BuyTicket implements Runnable{
    //票
    private int ticketNums = 10;
    boolean flag = true;//外部停止方式
    @Override
    public void run() {
        //买票
        while (flag){
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            try {
                buy();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
    //synchronized 同步方法，锁的是this
    private synchronized void buy() throws InterruptedException {
        //判断是否有票
        if(ticketNums<=0){
            return;
        }
        //模拟延时
        Thread.sleep(100);
        //买票
        System.out.println(Thread.currentThread().getName()+"-->"+ticketNums--);
    }
}

//不安全的取钱
//两个人去银行取钱，账户
public class Unsafebank {
    public static void main(String[] args) {
        //账户
        Account account = new Account(100, "结婚基金");
        Drawing you = new Drawing(account, 50, "你");
        Drawing wife = new Drawing(account, 100, "妻子");
        you.start();
        wife.start();
    }
}
//账户
class Account{
    int money;
    String name;//卡名
    public Account(int money, String name){
        this.money = money;
        this.name = name;
    }
}
//银行：模拟
class Drawing extends Thread{
    Account account;//账户
    //取了多少钱
    int drawingMoney;
    //现在手里有多少钱
    int nowMoney;

    public Drawing(Account account, int drawingMoney, String name){
        super(name);
        this.account = account;
        this.drawingMoney = drawingMoney;
    }
    //取钱
    //synchronized 默认锁定的是this
    public void run(){
        //锁定对象就是变化的量，需要增删改的对象
        synchronized(account){
            //判断有没有钱
            if (account.money-drawingMoney<0){
                System.out.println(Thread.currentThread().getName()+"钱不够，取不了");
                return;
            }
            //sleep可以放大问题的发生性
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            account.money = account.money - drawingMoney;
            nowMoney +=drawingMoney;
            System.out.println(account.name+"余额为："+account.money);
            //this.getName() = Thread.currentThread().getName()
            System.out.println(this.getName()+"手里的钱"+nowMoney);

        }

    }
}

机制锁 同步块 synchronized

方法声明用synchronized大大降低了代码效率

//测试JUC安全类型的集合
public class TestJUC {

    public static void main(String[] args) {
        CopyOnWriteArrayList list = new CopyOnWriteArrayList();
        for (int i = 0; i < 1000; i++) {
            new Thread(()->{
                list.add(Thread.currentThread().getName());
            }).start();
        }
        try {
            Thread.sleep(3000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        System.out.println(list.size());
    }
}

//死锁：多个线程互相抱着对方需要的资源，然后形成僵持
public class DeadLock {
    public static void main(String[] args) {
        Makeup g1 =new Makeup(0, "灰姑娘");
        Makeup g2 = new Makeup(1, "白雪公主");

        g1.start();
        g2.start();
    }
}
//口红
class Lipstick{

}
//镜子
class Mirror{

}
class Makeup extends Thread{

    //需要的资源只有一份，用static来保证只有一份
    static Lipstick lipstick = new Lipstick();
    static Mirror mirror = new Mirror();
    int choice;//选择
    String girlfriend;//使用化妆品的人
    Makeup(int choice ,String girlfriend){
        this.choice = choice;
        this.girlfriend = girlfriend;
    }
    @Override
    public void run() {
        //化妆
        try {
            makeup();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
    //化妆，互相持有对方的锁，就是需要拿到对方的资源
    private void makeup() throws InterruptedException {
        if (choice == 0){
            synchronized (lipstick){//获得口红的锁
                System.out.println(this.girlfriend+"获得口红的锁");
                Thread.sleep(1000);

            }
            synchronized (mirror){//一秒钟后想获得镜子
                System.out.println(this.girlfriend+"获得镜子的锁");
            }
        }else {
            synchronized (mirror){//获得镜子的锁
                System.out.println(this.girlfriend+"获得镜子的锁");
                Thread.sleep(1000);

            }
            synchronized (lipstick){//一秒钟后想获得口红
                System.out.println(this.girlfriend+"获得口红的锁");
            }
        }
    }
}

lock显示的锁，手动打开，手动关闭 syn锁是隐式的，出了作用域自动释放

lock效果更好

//测试lock锁
public class TestLock {
    public static void main(String[] args) {
        TestLock2 testLock2 = new TestLock2();

        new Thread(testLock2).start();
        new Thread(testLock2).start();
        new Thread(testLock2).start();
    }
}

class TestLock2 implements Runnable{
    int ticketNums = 10;

    //定义lock
    private final ReentrantLock lock = new ReentrantLock();

    @Override
    public void run() {
        while(true){
            try {
                lock.lock();//枷锁
                if (ticketNums>0){
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(ticketNums--);
                }else {
                    break;
                }
            }finally {
                //解锁
                lock.unlock();
            }

        }
    }
}

wait()#线程等待  会释放锁
notify()#唤醒处于等待状态的锁

方法一（管程法）：