为什么我的循环输入有误就直接跳过了呢？

for(int i=0;i<numberStudent;i++){
            System.out.println("Enter the grade for students " + (i+1)+":");
            int num = in.nextInt();
            while(num<0 || num>100){
                System.out.println("Invalid grade,try again");
                num = in.nextInt();
            }
            grade[i] = num;
            sum+=grade[i];
        }