java多线程如何实现1加到30

Question

java如何用10个线程实现从1加到100，如果不调用join每个线程都是从21开始加到30.求解决

 public class thread {

    public static void main(String[] args) throws InterruptedException {
        mythread mt = new mythread();

        mt.setbagin(1);
        Thread th1 = new Thread(mt,"第1个线程");
        th1.start();
        th1.join();

        mt.setbagin(11);
        Thread th2 = new Thread(mt,"第2个线程");
        th2.start();
        th2.join();

        mt.setbagin(21);
        Thread th3 = new Thread(mt,"第3个线程");
        th3.start();
        th3.join();

        System.out.println(mt.Getsum());
    }
}
class mythread extends Thread{
    public int sum=0;
    private int bagin;

    public void run(){//synchronized
        System.out.println(Thread.currentThread().getName()+"setbagin="+bagin);
        for(int i=bagin;i<=bagin+9;i++){
            sum+=i;
        System.out.println(Thread.currentThread().getName()+"sum:"+sum);
        }
    }

    public void setbagin(int bagin){
        this.bagin = bagin;
    }

    public int Getsum(){
        return sum;
    }
}

Answer 1

join() 方法主要是让调用改方法的thread完成run方法里面的东西后， 在执行join()方法后面的代码。
如果不加join()方法，程序并发执行，mt.setbagin(21);把在多线程执行前把前面的两次赋值都覆盖了。