Java多线程

创建多线程的四种方法继承Thread类

创建Thread的子类重写run方法(将创建线程做的事情写入到run方法中)创建Thread类的子类对象调用start方法

package eur1ka;

class MyThread extends Thread{
    @Override
    public void run() {
        for(int i = 0; i<100;i++){
            if(i%2==0){
                System.out.println(i);
            }

        }
    }
}

public class ThreadTest {
    public static void main(String[] args) {
        MyThread mythread = new MyThread();
        mythread.start();
    }
}

实现Runnable接口

创建一个实现了Runnable接口的类实现类去实现Runnable中的抽象方法创建实现类的对象将此方法作为参数传递到Thread类的构造器中，创建Thread类的对象通过Thread类的对象调用start()

package eur1ka;

public class Thread1 {
    public static void main(String[] args) {
        Thread1Test test = new Thread1Test();
        Thread t1 = new Thread(test);
        t1.start();
    }

}


class Thread1Test implements Runnable{

    @Override
    public void run() {
        for(int i = 0; i<100; i++){
            if(i%2==0){
                System.out.println(Thread.currentThread().getName()+":"+i);
            }
        }
    }
}

使用Callable接口特点

相对于Runnable，可以有返回值

方法可以抛出异常

支持泛型返回值

需要借助Future Task类，比如获取返回结果

Future

创建方法

1.创建一个实现Callable接口的类
2.实现call方法。即需要执行的函数，call方法有返回值
3.创建Callable接口实现类对象
4.创建FutureTask对象并将实现 callable接口的类传入
5.将FutureTask对象作为参数传入Thread构造器中

import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.FutureTask;

public class ThreadNew1 {
    public static void main(String[] args) {
        Threadnew t = new Threadnew();
        FutureTask ft = new FutureTask(t);
        Thread t1 = new Thread(ft);
        t1.start();
        try{
            Object sum = ft.get();
            System.out.println(sum);
        }catch (InterruptedException e) {
            e.printStackTrace();
        }catch(ExecutionException e){
                e.printStackTrace();
            }
        }
    }

class Threadnew implements Callable {

    @Override
    public Object call() throws Exception {
        int sum = 0;
        for(int i=0;i<100;i++){
            if(i%2==0){
                System.out.println(i);
                sum+=i;
            }
        }
        return sum;
    }
}

使用线程池

相关API：ExecutorService,Executors

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

public class ThreadPool {
    public static void main(String[] args) {
        ExecutorService executorService = Executors.newFixedThreadPool(10);
        executorService.execute(new NumThread());//适合使用Runnable
//        executorService.submit();//适合使用Callable
        executorService.shutdown();

    }
}
class NumThread implements Runnable{

    @Override
    public void run() {
        for(int i = 0;i<100;i++){
            if(i%2==0){
                System.out.println(Thread.currentThread().getName()+":"+i);
            }
        }
    }
}

多线程同步问题

方法1：同步监视器

synchronized(){}

需要监视的代码放到同步监视器中，与要注意的是同步监视器需要相同

方法2：同步方法

使用关键词synchronized声明为同步的

同步监视器 runnable接口

public class WindowsTest1 {
    public static void main(String[] args) {
        Windows1 w1 = new Windows1();
        Thread t1 = new Thread(w1);
        Thread t2 = new Thread(w1);
        Thread t3 = new Thread(w1);
        t1.start();
        t2.start();
        t3.start();
    }
}

class Windows1 implements Runnable{
    private int ticket=100;

    @Override
    public void run() {
        synchronized (this){
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            while(ticket>0) {
                System.out.println(Thread.currentThread().getName() + "=>当前票号为:" + ticket);
                ticket--;
            }
        }
    }
}

继承Thread类

public class WindowsTest3 {
    public static void main(String[] args) {
        Windows3 w1 = new Windows3();
        Windows3 w2 = new Windows3();
        Windows3 w3 = new Windows3();
        w1.start();
        w2.start();
        w3.start();
    }
}

class Windows3 extends Thread{
    private static int ticket=100;
    private static Object obj = new Object();
    @Override
    public void run() {
        while(true){
            synchronized (Windows3.class){
                if(ticket>0) {
                    try {
                        Thread.sleep(100);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + "=>当前票号为:" + ticket);
                    ticket--;
                }else{
                    break;
                }
            }
        }
    }
}

同步方法 Runnable接口

public class WindowsTest2 {
    public static void main(String[] args) {
        Windows2 w1 = new Windows2();
        Thread t1 = new Thread(w1);
        Thread t2 = new Thread(w1);
        Thread t3 = new Thread(w1);
        t1.start();
        t2.start();
        t3.start();
    }
}

class Windows2 implements Runnable{
    private int ticket=100;

    @Override
    public void run() {
        fun();


    }
    public synchronized void fun(){
        try {
            Thread.sleep(1000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        while(ticket>0) {
            System.out.println(Thread.currentThread().getName() + "=>当前票号为:" + ticket);
            ticket--;
        }

    }

}

继承Thread类

public class WindowsTest4 {
    public static void main(String[] args) {
        Windows4 w1 = new Windows4();
        Windows4 w2 = new Windows4();
        Windows4 w3 = new Windows4();
        w1.start();
        w2.start();
        w3.start();
    }
}

class Windows4 extends Thread{
    private static int ticket=100;
    private static Object obj = new Object();
    @Override
    public void run() {
        while(true){
            fun();
            }
        }
    public static synchronized void fun(){
        while(ticket>0) {
            try {
                Thread.sleep(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(Thread.currentThread().getName() + "=>当前票号为:" + ticket);
            ticket--;
        }
    }

}

实例化ReentrantLock

实例化reentrantlock调用lock方法解锁

import java.util.concurrent.locks.ReentrantLock;

public class LockTest {
    public static void main(String[] args) {
        Windows w1 = new Windows();
        Thread t1 = new Thread(w1);
        Thread t2 = new Thread(w1);
        Thread t3 = new Thread(w1);
        t1.start();
        t2.start();
        t3.start();
    }

}

class Windows implements Runnable{
    private int ticket = 100;
    // 实例化reentrantlock
    private ReentrantLock lock = new ReentrantLock(true);

    @Override
    public void run() {
        try{
            //调用lock方法
            lock.lock();
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            while(ticket>0) {
                System.out.println(Thread.currentThread().getName() + "=>当前票号为:" + ticket);
                ticket--;
            }
        }finally {
            //解锁
            lock.unlock();
        }
    }
}

Java多线程

Java相关栏目本月热门文章