当计时器结束时，程序不会结束，直到您输入为止

Question

我有一些空闲时间，我决定制作一个程序，可以使用Java Eclipse给我数学问题。无论何时计时器结束，while循环都不会结束，直到你给出最后一个输入。我知道这是因为while循环，但我不知道如何结束它。

import java.util.Random;
import java.util.Scanner;
public class math_questioner_4 {
    public static void main(String[] args) {
        int firstnumber,secondnumber,operation,answer,answerinput,correctcount = 0,incorrectcount = 0, time, difficulty, max = 0, mixedop;
        Scanner input;
        System.out.println("What do you want the operation to be? 1 = addition 2 = subtraction 3 = multiplication 4 = division 5 = mixed");
        input = new Scanner(System.in);
        operation = input.nextInt();
        // There is around 30 lines that don't relate to the question here
        if (operation == 1) {
            long endTime = System.currentTimeMillis() + (time*1000);
            while (System.currentTimeMillis() < endTime) {
                Random rand = new Random();
                firstnumber = rand.nextInt(max) + 1;
                secondnumber = rand.nextInt(max) + 1;
                answer = firstnumber + secondnumber;
                System.out.println("What is " + firstnumber + " + " + secondnumber + "?");
                answerinput = input.nextInt();
                if (answerinput == answer) {
                    System.out.println("Correct!");
                    correctcount++;
                } else {
                    System.out.println("Sorry, " + firstnumber + " + " + secondnumber + " is " + answer + ".");
                    incorrectcount++;
                }
            }
        // Another 140 lines here that don't matter either, just some operations
        if (time == 1) {
            System.out.println("You got " + correctcount + " questions correct and " + incorrectcount + " wrong in " + time + " second!");
        } else {
            System.out.println("You got " + correctcount + " questions correct and " + incorrectcount + " wrong in " + time + " seconds!");
        }
    }
}

我知道它是因为它不会结束的while循环，但我不知道如何。也请不要对我大喊大叫。我是一个在我的中文学校上课的初学者，这只是我的第9周（我已经去过9个班级），这是随机的额外内容。我从这个网站得到了大部分答案，我也学会了用整数做事。这也是我的第一个问题。