53 Math类的静态方法

import java.util.Scanner;  //  错误写成 until

class GuessNum{
    public static void main(String[] args) {
        Scanner sr  =  new Scanner(System.in);
        System.out.println("please input a number betwean 1 to 200");
        // int num = sr.nextInt();  // 错误 这样while循环就只针对一个值了
        int guessNum = (int)(Math.random()*100+1);   // random是Math的静态方法,忘记写()

        while(true){
            int num = sr.nextInt();
            if(guessNum > num ){
                System.out.println("小了");
            }else if(guessNum < num){
                System.out.println("大了");
            }else{
                System.out.println("中了");
                break;
            }
        }
    }
}