线程的创建

方式一：Thread

public class dome {
    public static void main(String[] args) {
        MyThread myThread = new MyThread();
        myThread.start();
        for(int i=1;i<=5;i++){
            System.out.println("主线程"+i);
        }
    }
}

public class MyThread extends Thread{
    @Override
    public void run() {
        for(int i=0;i<5;i++){
            System.out.println("MyThread线程"+i);
        }
    }
}

方式二：Runnable

public class dome {
    public static void main(String[] args) {
        Runnable r = new MyRunnable();
        new Thread(r).start();
        for(int i=1;i<=5;i++){
            System.out.println("主线程"+i);
        }
    }
}

public class MyRunnable implements Runnable{
    @Override
    public void run() {
        for(int i=1;i<=5;i++){
            System.out.println("MyRunnable"+i);
        }
    }
}

方式三：Callable

public class dome {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        //3.创建一个Callable对象
        Callable c = new MaCallable(100);
        //4.把Callable对象封装成一个FutureTask对象（任务对象）
        FutureTask<String> f = new FutureTask<>(c);

        //作用
        //1.是一个任务对象，实现了Ruuable类
        //2.可以用get()方法获取任务执行完后的结果
        new Thread(f).start();

        //获取执行完之后的结果
        //如果此时还未执行完，则在此等待
        String s = f.get();
        System.out.println(s);
    }
}

//1.实现Callable接口
public class MaCallable implements Callable<String> {
    private int n;
    public MaCallable(int n){
        this.n=n;
    }
    //2.重写call方法

    @Override
    public String call() throws Exception {
        int sum=0;
        for(int i=1;i<=n;i++){
            sum+=i;
        }
        return "1-"+n+"的和为："+sum;
    }
}

Thread常用方法

public class dome {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        Thread t1 = new MyThread("1号");
//        t1.setName("1号");//设置线程名称
        t1.start();

        Thread t2 = new MyThread("2号");
//        t1.setName("2号");
        t2.start();

        Thread t = Thread.currentThread();
        for(int i=1;i<=5;i++){
            System.out.println(t.getName()+"线程"+i);
        }
    }
}

public class MyThread extends Thread{
    public MyThread(String name){
        super(name);
    }
    @Override
    public void run() {
        Thread t = Thread.currentThread();//用来获取线程名称
        for(int i=0;i<5;i++){
            System.out.println(t.getName()+"线程"+i);
        }
    }
}

 

public class dome {
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        for(int i=1;i<=5;i++){
            if(i==3){
                //休眠5秒
                Thread.sleep(5000);
            }
            System.out.println(i);
        }

        //join：让当前线程先跑完
        Thread t1 = new MyThread("1号");
        t1.start();
        t1.join();
        
        Thread t2 = new MyThread("2号");
        t2.start();

        Thread t3 = new MyThread("3号");
        t3.start();
        t2.join();
    }
}

线程同步

线程安全

线程同步的几种方式

1.同步代码块 （比2好）

    public void dr(int n) {
        String name = Thread.currentThread().getName();
        synchronized (this) {
            //实力方法建议用this,静态方法建议用。class
            if(n<=num){

                System.out.println(name+"取钱"+n);
                num-=n;
                System.out.println(name+"剩"+num);
            }
            else {
                System.out.println(name+"不足");
            }
        }
    }

2.同步方法（可读性好）

 public synchronized void dr(int n) {
        String name = Thread.currentThread().getName();
            if(n<=num){

                System.out.println(name+"取钱"+n);
                num-=n;
                System.out.println(name+"剩"+num);
            }
            else {
                System.out.println(name+"不足");
            }
    }