JAVA复习之线程

一、线程

二、线程的特点

三、线程的生命周期

四、Thread类

Thread类是java.lang包中的一个类，Thread类的对象用来代表线程，通过继承Thread类创建、启动并执行一个线程的步骤：①创建一个继承Thread类的子类；②覆写Thread类的run()方法；③创建线程类的一个对象；④通过线程类的对象调用start()方法启动线程(启动之后会自动调用覆写的run()方法执行线程)。

案例分析：

public class Demo5 {
    public static void main(String[] args) {
        ThreadA threadA = new ThreadA();
        threadA.start();
        ThreadB threadB = new ThreadB();
        threadB.start();
    }
}
class ThreadA extends Thread{
    public void run(){
        for(int i=0;i<100;i++){
            System.out.println(i);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}
class ThreadB extends Thread{
    public void run(){
        for(char i= 'a';i<'z';i++){
            System.out.println(i);
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }
}

五、Runnable接口

六、线程的休眠

七、线程的加入

八、线程的中断

九、线程的安全

（一）案例之线程不安全，出现脏读

public class Demo6 implements Runnable{
    int num = 10;
    public static void main(String[] args) {
        Demo6 demo = new Demo6();
        Thread t1 = new Thread(demo,"线程一");
        Thread t2 = new Thread(demo,"线程二");
        Thread t3 = new Thread(demo,"线程三");
        Thread t4 = new Thread(demo,"线程四");
        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
    @Override
    public void run() {
        while (true){
            if(num>0){
                System.out.println("票数："+num--);
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }
}

（二）线程同步机制synchronized关键字

两种方法：

案例剖析：

public class Demo6 implements Runnable{
    int num = 10;
    public static void main(String[] args) {
        Demo6 demo = new Demo6();
        Thread t1 = new Thread(demo,"线程一");
        Thread t2 = new Thread(demo,"线程二");
        Thread t3 = new Thread(demo,"线程三");
        Thread t4 = new Thread(demo,"线程四");
        t1.start();
        t2.start();
        t3.start();
        t4.start();
    }
    @Override
    public void run() {
        while (true){
            synchronized (this){
                if(num>0){
                    System.out.println("票数："+num--);
                    try {
                        Thread.sleep(1000);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }
}