Java多线程

进程

线程

多线程实现方式

public class MyThread extends Thread{
    @Override
    public void run() {
        for (int i = 0; i<100; i++){
            System.out.println(i);
        }
    }
}

public class ThreadDemo1 {
    public static void main(String[] args) {
    MyThread myThread=new MyThread();
    MyThread myThread1=new MyThread();

//    myThread.run();
//    myThread1.run();

    //void start():导致线程开始执行 Java虚拟机开始调用此线程的run方法
        myThread.start();
        myThread1.start();
    }
}

如果打印结果仍然一样，说明cou太好了，把循环次数改为1000试试

设置和获取线程名称

public class MyThread extends Thread{
    @Override
    public void run() {
        for (int i = 0; i<100; i++){
//            System.out.println(i);
            //String getName():返回此线程的名称
            System.out.println(getName()+":"+i);
        }
    }
}

public class ThreadDemo1 {
    public static void main(String[] args) {
    MyThread myThread=new MyThread();
    MyThread myThread1=new MyThread();

//    myThread.run();
//    myThread1.run();

        //setName(String name):将此线程名称更改为参数name
        myThread.setName("高铁");
        myThread.setName("飞机");

    //void start():导致线程开始执行 Java虚拟机开始调用此线程的run方法
        myThread.start();
        myThread1.start();
    }
}

public class ThreadDemo1 {
    public static void main(String[] args) {
//    MyThread myThread=new MyThread();
//    MyThread myThread1=new MyThread();
//
    myThread.run();
    myThread1.run();
//
//        //setName(String name):将此线程名称更改为参数name
//        myThread.setName("高铁");
//        myThread1.setName("飞机");
//
//
//
//    //void start():导致线程开始执行 Java虚拟机开始调用此线程的run方法
//        myThread.start();
//        myThread1.start();

        //static Thread currentThread():返回当前正在执行对象的引用
        System.out.println(Thread.currentThread().getName());
    }
}

线程优先级

public class ThreadDemo1 {
    public static void main(String[] args) {
    MyThread myThread=new MyThread();
    MyThread myThread1=new MyThread();

//    myThread.run();
//    myThread1.run();

        //setName(String name):将此线程名称更改为参数name
        myThread.setName("高铁");
        myThread1.setName("飞机");

        //public final int getPriority():返回此线程的优先级
        System.out.println(myThread.getPriority());//5
        System.out.println(myThread1.getPriority());//5

        //public fina; void setPriority(int newPriority):更改此线程的优先级
//        myThread.setPriority(100);//IllegalArgumentException异常 不能超出MAX_PRIORITY 不能低于MIN_PRIORITY 默认值NORM_PRIORITY
        System.out.println(Thread.MAX_PRIORITY);//10
        System.out.println(Thread.MIN_PRIORITY);//1
        System.out.println(Thread.NORM_PRIORITY);//5

        myThread.setPriority(10);
        myThread1.setPriority(1);

        //void start():导致线程开始执行 Java虚拟机开始调用此线程的run方法
        myThread.start();
        myThread1.start();

        //static Thread currentThread():返回当前正在执行对象的引用
//        System.out.println(Thread.currentThread().getName());
    }
}

线程控制

public class MyThread extends Thread{
    @Override
    public void run() {
        for (int i = 0; i<100; i++){
//            System.out.println(i);
            //String getName():返回此线程的名称
            System.out.println(getName()+":"+i);
            try {
            //static void sleep(long millis):使当前正在执行的线程(暂停执行)指定的毫秒数
               Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

运行ThreadDemo1

线程声明周期

实现Runnable接口的方式实现多线程

public class MyRunnable implements Runnable{
    @Override
    public void run() {
        for(int i=0; i<100; i++){
            System.out.println(Thread.currentThread().getName()+":"+i);
        }
    }
}

public class MyRunnableDemo {
    public static void main(String[] args) {
        MyRunnable myRunnable=new MyRunnable();

        //创建Tread类对象 把MyRunnable对象作为构造方法的参数
        //Thread(Runnable target)
//        Thread t1=new Thread(myRunnable);

        //Thread(Runnable target, String name)
        Thread t1=new Thread(myRunnable,"高铁");
        Thread t2=new Thread(myRunnable,"飞机 ");

        //启动线程
        t1.start();
        t2.start();
    }
}

案例：火车卖票

 	public class SellTicket implements Runnable{
    private int ticket=100;
    @Override
    public void run() {
        //相同的票出现了多次
        while(true) {
            //ticket=100
            //t1 t2 t3
            //假设t1抢到了CPU的执行权
            if (ticket > 0) {
                //通过sleep()方法实现出票时间
                try {
                    Thread.sleep(100);
                    //t1休息100毫秒
                    //假设t2抢到CPU的执行权 运行到这里 休息100毫秒
                    //t3抢到CPU的执行权  运行到这里 休息100毫秒
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                //假设线程顺序按照顺序醒过来
                //t1抢到CPU执行权 在控制台输出 窗口1正在出售第100张票
                //t2抢到CPU执行权 在控制台输出 窗口2正在出售第100张票
                //t3抢到CPU执行权 在控制台输出 窗口3正在出售第100张票
                System.out.println(Thread.currentThread().getName() + "正在出售第" + ticket + "张票");
                ticket--;
                //假设这三个线程还是按照顺序来 就执行了三次ticket--操作 最终票数变成了97
            }
        }

    }
}

public class SellTicketTest {
    public static void main(String[] args) {
        SellTicket sellTicket=new SellTicket();

        Thread t1=new Thread(sellTicket,"窗口1");
        Thread t2=new Thread(sellTicket,"窗口2");
        Thread t3=new Thread(sellTicket,"窗口3");

        //启动线程
        t1.start();
        t2.start();
        t3.start();


    }
}

线程同步

修改文件

public class SellTicket implements Runnable{
    private int ticket=100;
    private Object obj=new Object();

    @Override
    public void run() {
        while(true) {
            synchronized (obj) {
                if (ticket > 0) {
                    //通过sleep()方法实现出票时间
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "正在出售第" + ticket + "张票");
                    ticket--;
                }
            }
        }
    }
}

同步方法

public class SellTicket implements Runnable{
    private int ticket=100;
    private Object obj=new Object();
    private int x=0;

    @Override
    public void run() {
        while(true) {
            if (x%2==0) {
                synchronized (obj) {
                    if (ticket > 0) {
                        //通过sleep()方法实现出票时间
                        try {
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                        System.out.println(Thread.currentThread().getName() + "正在出售第" + ticket + "张票");
                        ticket--;
                    }
                }
            }
            else {
                sellTicket();
            }
            x++;
        }
    }

    private synchronized void  sellTicket() {
            if (ticket > 0) {
                //通过sleep()方法实现出票时间
                try {
                    Thread.sleep(100);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                System.out.println(Thread.currentThread().getName() + "正在出售第" + ticket + "张票");
                ticket--;
        }
    }
}

线程安全的类

StringBuffer
Vector
Hashtable

Lock锁

修改文件

public class SellTicket implements Runnable{
    private int ticket=100;
    private Lock lock=new ReentrantLock();

    @Override
    public void run() {
        while (true) {
            try {
                lock.lock();
                if (ticket > 0) {
                    //通过sleep()方法实现出票时间
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "正在出售第" + ticket + "张票");
                    ticket--;
                }
            }finally {
                lock.unlock();
            }
        }
    }
}

生产者消费者模式概述

Java多线程

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