Java线程求和

public class ThreadAdd extends Thread {
    private int stratNum;
    private static int sum;
    //构造方法
    public  ThreadAdd(int stratNum) {
        this.stratNum = stratNum;
    }
    public static synchronized void add(int num) {
        sum += num;
    }
    //重载run方法
    @Override
    public void run() {
        int sum = 0;
        for (int i = 0; i < 10; i++) {
            sum += stratNum + i;
        }
        add(sum);
    }
    //主线程
    public static void main(String[] args) {
        Thread[] threadlist = new Thread[10];
        for (int i = 0; i < 10; i++) {
            threadlist[i] = new ThreadAdd(10 * i + 1);//1 11 21  31 41 51 61 71 81 91
            threadlist[i].start();//开启线程
        }
        System.out.println("Sum is ：" + sum);
    }
}