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Java多线程基础一

Java多线程基础一

作者: 有斧头的IceBear | 来源:发表于2020-08-11 00:11 被阅读0次

    多线程创建的三种方式

    image6.png 
    //创建线程方式一：继承Thread类，重写run()方法，调用start开启线程
//总结：注意，线程开启不一定立即执行，由CPU调度执行
public class TestThread1 extends Thread {
    //ctrl + O 实现接口方法
    @Override
    public void run() {
        //20.for
        //run方法线程体
        for (int i = 0; i < 2000; i++) {
            System.out.println("我在看代码" + i);
        }
    }

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

        //创建一个线程对象
        TestThread1 testThread1 = new TestThread1();

        //调用start()方法开启线程
        testThread1.start();

        for (int i = 0; i < 2000; i++) {
            System.out.println("我在学习多线程" + i);
        }
    }
}

    //练习Thread，实现多线程同步下载图片
public class TestThread2 implements Runnable {

    private String url;
    private String name;

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

    //下载图片执行体
    @Override
    public void run() {
        WebDownLoader webDownLoader = new WebDownLoader();
        webDownLoader.downloader(url, name);
        System.out.println("下载了文件名为" + name);
    }

    public static void main(String[] args) {
        TestThread2 t1 = new TestThread2("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1596570590398&di=6cf133c3e5c91ecee840f29d138f8d3e&imgtype=0&src=http%3A%2F%2Fdepot.nipic.com%2Ffile%2F20150630%2F13214150_10223002228.jpg", "1.jpg");
        TestThread2 t2 = new TestThread2("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1596570971558&di=732d6b6458d6be119c5b9ba8206b7a53&imgtype=0&src=http%3A%2F%2Fimg02.tooopen.com%2Fimages%2F20150612%2Ftooopen_sy_130061294574.jpg", "2.jpg");
        TestThread2 t3 = new TestThread2("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1596571028542&di=68cb54fdea5116f7760c4d1f543b0f5c&imgtype=0&src=http%3A%2F%2Fhbimg.huabanimg.com%2F828f2b88f2105989fdc04e82b7dd21d68d34132b10a5a-c8Ei6W_fw658", "3.jpg");

        new Thread(t1).start();
        new Thread(t2).start();
        new Thread(t3).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，downloader方法出现问题");
        }
    }
}

    //创建线程方式二：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 TestThread3 implements Runnable {
    //ctrl + O 实现接口方法
    @Override
    public void run() {
        //20.for
        //run方法线程体
        for (int i = 0; i < 2000; i++) {
            System.out.println("我在看代码" + i);
        }
    }

    public static void main(String[] args) {
        //创建runnable接口的实现类对象

        TestThread3 testThread3 = new TestThread3();

        //创建线程对象，通过线程对象来开启我们的线程，代理
        new Thread(testThread3).start();

        for (int i = 0; i < 2000; i++) {
            System.out.println("我在学习多线程" + i);
        }
    }
}

    //多个线程同时操作同一对象
//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
    private int ticketNums = 10;

    @Override
    public void run() {

        while (true) {
            if (ticketNums <= 0) {
                break;
            }

            //模拟延时
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            System.out.println(Thread.currentThread().getName() + "-->拿到了第" + ticketNums-- + "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, "黄牛").start();
    }
}
    image1.png 
    //线程创建方式三：实现callable接口
/*
 callable的好处
 1.可以定义返回值
 2.可以抛出异常
 */
public class TestCallable implements Callable<Boolean> {
    private String url;
    private String name;

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

    //下载图片执行体
    @Override
    public Boolean call() {
        WebDownLoader webDownLoader = new WebDownLoader();
        webDownLoader.downloader(url, name);
        System.out.println("下载了文件名为" + name);
        return true;
    }

    public static void main(String[] args) throws ExecutionException, InterruptedException {
        TestCallable t1 = new TestCallable("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1596570590398&di=6cf133c3e5c91ecee840f29d138f8d3e&imgtype=0&src=http%3A%2F%2Fdepot.nipic.com%2Ffile%2F20150630%2F13214150_10223002228.jpg", "1.jpg");
        TestCallable t2 = new TestCallable("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1596570971558&di=732d6b6458d6be119c5b9ba8206b7a53&imgtype=0&src=http%3A%2F%2Fimg02.tooopen.com%2Fimages%2F20150612%2Ftooopen_sy_130061294574.jpg", "2.jpg");
        TestCallable t3 = new TestCallable("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1596571028542&di=68cb54fdea5116f7760c4d1f543b0f5c&imgtype=0&src=http%3A%2F%2Fhbimg.huabanimg.com%2F828f2b88f2105989fdc04e82b7dd21d68d34132b10a5a-c8Ei6W_fw658", "3.jpg");

        //创建执行服务
        ExecutorService ser = Executors.newFixedThreadPool(3);

        //提交执行
        Future<Boolean> r1 = ser.submit(t1);
        Future<Boolean> r2 = ser.submit(t2);
        Future<Boolean> r3 = ser.submit(t3);

        //获取结果
        boolean rs1 = r1.get();
        boolean rs2 = r2.get();
        boolean rs3 = r3.get();

        System.out.println(rs1);
        System.out.println(rs2);
        System.out.println(rs3);

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

//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，downloader方法出现问题");
        }
    }
}
    image2.png 
    //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
//代理对象要代理真实角色

//好处：
    //代理对象可以做很多真实对象做不了的事情
    //真实对象专注做自己的事情

public class StaticProxy {
    public static void main(String[] args) {
        You you = new You();  //你要结婚

        new Thread( ()-> System.out.println("hello world") ).start();

        new WeddingCompany(new You()).HappyMarry();
        WeddingCompany weddingCompany = new WeddingCompany(you);
        weddingCompany.HappyMarry();
    }

}

interface Marry{
    void HappyMarry();
}

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

//代理角色，帮助你结婚
class WeddingCompany implements Marry {

    //代理谁--》真实是目标角色
    private Marry target;

    public WeddingCompany(Marry target) {
        this.target = target;
    }

    @Override
    public void HappyMarry() {
        before();
        this.target.HappyMarry();  //这就是真是对象
        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，收尾款");
    }

}

    lambda

    image3.png image4.png image5.png 
    /*
推导lambda表达式
*/
public class TestLambda1 {
    //3.静态内部类
    static class Like2 implements ILike {
        @Override
        public void lambda() {
            System.out.println("i like lambda2");
        }
    }

    public static void main(String[] args) {
        //创建一个接口对象
        ILike like = new Like();
        like.lambda();

        like = new Like2();
        like.lambda();

        //4.局部内部类
        class Like3 implements ILike {
            @Override
            public void lambda() {
                System.out.println("i like lambda3");
            }
        }

        like = new Like3();
        like.lambda();

        //5.匿名内部类，没有类的名称，必须借助接口或者父类
        like = new ILike() {
            @Override
            public void lambda() {
                System.out.println("i like lambda4");
            }
        };
        like.lambda();

        //6.用lambda简化
        like = () -> {
            System.out.println("i like lambda5");
        };
        like.lambda();
    }
}

//1.定义一个函数式接口
interface ILike {
    void lambda(); //在接口里隐式声明为一个抽象方法
}

//2.实现类
class Like implements ILike {
    @Override
    public void lambda() {
        System.out.println("i like lambda");
    }
}

    public class TestLambda2 {

    public static void main(String[] args) {

        //1.lambda表示简化
        ILove love = (int a) -> {
                System.out.println("i love you-->" + a);
        };

        //简化1.参数类型
        love = (a) -> {
            System.out.println("i love you-->" + a);
        };

        //简化2.简化括号
        love = a -> {
            System.out.println("i love you-->" + a);
        };

        //简化3.去掉花括号
        love = a -> System.out.println("i love you-->" + a);
        love.love(521);

        //总结：
            //lambda表达式只能有一行代码的情况下才能简化成一行，如果有多行，那么就用代码包裹。
            //前提是接口为函数式接口
            //多个参数也可以去掉参数类型，要去掉就都去掉，必须加上括号
    }
}

interface ILove {
    void love(int a);
}

class Love implements ILove {
    @Override
    public void love(int a) {
        System.out.println("i love you-->" + a);
    }
}

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