java多线程

一.多线程,多进程

一个进程可以有多个线程

二.线程的创建

1.Thread class

(继承自Thread类 重点)

package com.codelorni.demo;

public class TestThread 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) {
        TestThread testThread = new TestThread();
        testThread.start();

        for (int i = 0; i < 20; i++) {
            System.out.println("我在学习多线程"+i);
        }
    }

}

2.Runnable接口

(实现 Runnable 接口 重点)

package com.codelorni.demo;

public class TestThread implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 200; i++) {
            System.out.println("我在看代码");
        }
    }

    public static void main(String[] args) {
        TestThread testThread = new TestThread();
        //通过线程对象开启我们的线程,代理
//        Thread thread = new Thread(testThread);
//        thread.start();
        //等价于下面
        new Thread(testThread).start();
        for (int i = 0; i < 1000; i++) {
            System.out.println("我在学习多线程");
        }
    }
}

3.Callable 接口

(实现 Callable接口 了解)

package com.codelorni.demo;

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class TestThread implements Callable<Boolean> {


    @Override
    public Boolean call() throws Exception {
        return null;
    }
    public static void main(String[] args) {
        TestThread testThread = new TestThread();
		//执行创建任务
        ExecutorService ser = Executors.newFixedThreadPool(3);
		//提交执行
        Future<Boolean> result = ser.submit(testThread);
        //获取结果
        boolean r1 = result.get();
        //结束
        ser.shutdownNow();
    }
}

三.并发问题

1.初时并发问题

package com.codelorni.demo;

public class TestThread implements Runnable {
    private int ticketNums = 10;

    @Override
    public void run() {
        while (true) {
            if (ticketNums <= 0) {
                break;
            }
            try {
                Thread.sleep(200);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "拿到了第" + ticketNums-- + "张票");

        }
    }

    public static void main(String[] args) {
        TestThread testThread = new TestThread();

        new Thread(testThread, "小明").start();
        new Thread(testThread, "小李").start();
        new Thread(testThread, "小张").start();

    }


}
//多个线程操作同一个资源,线程不安全,数据紊乱

四.静态代理模式

1. 真实对象和代理对象都要实现同一个接口
2. 代理对象要代理真实对象
3. 代理对象可以做真实对象做不了的事情
4. 真实对象专注做自己的事情

package com.codelorni.demo;

public class StaticProxy {
    public static void main(String[] args) {
        MarryProxy marryProxy = new MarryProxy(new You());
        marryProxy.happyMarry();
    }

}

interface Marry {
    void happyMarry();
}

class You implements Marry {

    @Override
    public void happyMarry() {
        System.out.println("happy marry!");
    }
}

class MarryProxy implements Marry {
    private Marry target;

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

    @Override
    public void happyMarry() {
        before();
        this.target.happyMarry();
        after();
    }

    private void before() {
        System.out.println("before");
    }

    private void after() {
        System.out.println("after");
    }


}

五.Lambda表达式

• 避免匿名内部类定义过多
• 可以让你的代码开起来很简洁
• 去掉了一堆没有意义的代码

接口只包含一个抽象方法,那么它就是函数式接口

package com.codelorni.demo;

public class TestLambda {
    //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) {
        Like like = new Like();
        like.lambda();

        Like2 like2 = new Like2();
        like2.lambda();

        //局部内部类
        class Like3 implements ILike {

            @Override
            public void lambda() {
                System.out.println("i like lambda3!!!");
            }
        }
        Like3 like3 = new Like3();
        like3.lambda();

        //匿名内部类
       ILike like4 = new ILike() {

            @Override
            public void lambda() {
                System.out.println("i like lambda4!!!");
            }
        };
       like4.lambda();

//        lambda
        ILike like5 = () -> {
            System.out.println("i like lambda3!!!");
        };
        like5.lambda();

    }
}

interface ILike {
    void lambda();
}

class Like implements ILike {

    @Override
    public void lambda() {
        System.out.println("i like lambda!!!");
    }
}