如何在if / else語句中添加while循環

Question

我正在嘗試為此程序添加一個while循環。 到目前為止，它會生成2個隨機數，用戶必須輸入數字的乘積。 現在，用戶每次必須重新運行該程序。 目標是讓用戶繼續此操作，直到他們決定通過輸入前哨值-1來停止。 我是否應該將while循環放在if語句上方？

  Random random = new Random();
  Scanner scan = new Scanner(System.in);

  final int SENTINEL = -1;
  int number1 = random.nextInt(13);
  int number2 = random.nextInt(13);
  int answer = number1 * number2;

  System.out.print("What is " + number1 + " X " + number2 + "? > ");
  int product = scan.nextInt(); 

  if (product == answer) {
    System.out.println("Correct! " + number1 + " X " + number2 + " = " + answer);
  } else { 
     System.out.println("Wrong " + number1 + " X " + number2 + " = " + answer);
  }

Answer 1

如果希望用戶每次獲得一個新的隨機生成的數字，則while循環應該在生成隨機數之前進行。 換一種說法：

Random random = new Random();
Scanner scan = new Scanner(System.in);

final int SENTINEL = -1;
int number1;
int number2;
int product = 0;

while (product != SENTINEL) {
  number1 = random.nextInt(13);
  number2 = random.nextInt(13);
  int answer = number1 * number2;

  System.out.print("What is " + number1 + " X " + number2 + "? > ");
  product = scan.nextInt(); 

  if (product == answer) {
    System.out.println("Correct! " + number1 + " X " + number2 + " = " + answer);
  } else { 
    System.out.println("Wrong " + number1 + " X " + number2 + " = " + answer);
  }
}

通常，while語句應放在要重復的代碼的第一部分之前。

Answer 2

像這樣：

while(true){
  number1 = random.nextInt(13);
  number2 = random.nextInt(13);
  int answer = number1 * number2;
  System.out.print("What is " + number1 + " X " + number2 + "? > ");
  int product = scan.nextInt(); 

  if(product == SENTINEL){
     System.exit(0);  // you could also use break; here
  }
  if (product == answer) {
    ...
}