int testGrade = -1 ;Scanner studentInput = new Scanner(System.in);while (testGrade > 100 || testGrade < 0) { System.out.println("Your input does not match the criteria, please enter a number between 0 and 100"); while(!studentInput.hasNextInt()) { studentInput.next() ; } testGrade = studentInput.nextInt();}有一个无限循环来检查流中是否有无效字符。如果是这样，那就食用它，这就是
hasNextInt()目的。如果输入有效内容，则该循环退出。
