Java 产生一个大于等于200，小于300的随机数，且是10的整数倍

 public class Random200_300 {
     public static void main(String[] args) {
         int r1 = 0;
         while (true) {
             r1 = (int)(Math.random() * 10) * 10 + 200;
             if ((200 <= r1) && (r1 < 300)) {
                 System.out.println(r1);
             } else {
                 System.out.println("Error!");
                 break;
             }

             try {
                 Thread.sleep(200);
             } catch (InterruptedException e) {
                 e.printStackTrace();
             }
         }
     }
 }