所以我沒有意識到程序正在運行，只是空白，因為java讀取下來了，系統在我看到答案之前一直在等我輸入答案。謝謝@wdc的幫助。原來的我目前正在練習Java，遇到了一個已解決的問題，但我不明白為什么，當我有這樣的程序時，程序如何運行：import java.util.Scanner;public class Practice {    public static void main(String[] args) {        Scanner in = new Scanner(System.in);        int number1 = (int)(System.currentTimeMillis() % 10);        int number2 = (int)(System.currentTimeMillis() / 10 % 10);        System.out.print("What is " +  number1 + " + " + number2 + "?");        int answer = in.nextInt();        System.out.println(number1 + " + " + number2 + " = " + answer + " is " + (number1 + number2 == answer));    }}但是當我有這樣的時候是行不通的：import java.util.Scanner;public class Practice {    public static void main(String[] args) {            Scanner in = new Scanner(System.in);            int number1 = (int)(System.currentTimeMillis() % 10);            int number2 = (int)(System.currentTimeMillis() / 10 % 10);            int answer = in.nextInt();            System.out.print("What is " +  number1 + " + " + number2 + "?");            System.out.println(number1 + " + " + number2 + " = " + answer + " is " + (number1 + number2 == answer));        }    }我想知道，這樣我以后就可以避免這個問題。