java多线程的实现以及如何保持线程安全

一、java多线程实现的两种方式

一、继承Thread

/**
 * 
 * @version: 1.1.0
 * @Description: 多线程
 * @author: wsq
 * @date: 2020年6月8日下午2:25:33
 */
public class MyThread extends Thread{
@Override
public void run() {
    System.out.println("This is the first thread!");
}
public static void main(String[] args) {
    MyThread mt = new MyThread();
    mt.start();
}
}

二、实现 Runnable 接口

public class MultithreadingTest {
public static void main(String[] args) {
    new Thread(() -> System.out.println("This is the first thread!")).start();
}
}

或者

public class MyThreadImpl implements Runnable{
private int count = 5;
    @Override
    public void run() {
        // TODO Auto-generated method stub
        count--;
        System.out.println("Thread"+Thread.currentThread().getName()+"count:"+count);
    }
}

二、解决线程不安全问题

/**
 * 
 * @version: 1.1.0
 * @Description: 测试类
 * @author: wsq
 * @date: 2020年6月8日下午9:27:02
 */
public class Test {
    public static void main(String[] args) {
        MyThreadImpl myThreadImpl = new MyThreadImpl();
        Thread A = new Thread(myThreadImpl,"A");
        Thread B = new Thread(myThreadImpl,"B");
        Thread C = new Thread(myThreadImpl,"C");
        Thread D = new Thread(myThreadImpl,"D");
        Thread E = new Thread(myThreadImpl,"E");
        A.start();
        B.start();
        C.start();
        D.start();
        E.start();
    }
}

打印结果为：

ThreadBcount:3
ThreadCcount:2
ThreadAcount:3
ThreadDcount:1
ThreadEcount:0

B和A共用一个线程，存在线程安全问题

改成：

public class MyThreadImpl implements Runnable{
private int count = 5;
    @Override
　　// 使用同步解决线程安全问题
    synchronized public void run() {
        // TODO Auto-generated method stub
        count--;
        System.out.println("Thread"+Thread.currentThread().getName()+"count:"+count);
    }
}