while 循環嵌套 if else java

Question

我的 while 循環有問題。 它需要不斷提出問題，直到答案正確為止。 有人可以建議嗎？

public class QuizW
{
    public static void main(String[] args)
    {
        String question = "What is the capital of Australia? \n";
        question += "A. Sydney\n";
        question += "B. Melburne\n";
        question += "C. Perth\n";
        question += "D. Cannberra\n";
        question += "E. Brisbane\n";

        String answer = JOptionPane.showInputDialog(question);
        answer = answer.toUpperCase();
        int answerCorrect = 0;
        
        while (answerCorrect == 0)
        {
            if (answer.equals("D"))
            {
                JOptionPane.showMessageDialog(null, "Correct!");
                break;
            }
            else if (answer.equals("A") || answer.equals("B") || answer.equals("C") || answer.equals("E"))
            {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again.");
            }
            else
            {
                JOptionPane.showMessageDialog(null, "Invalid answer. Please enter A, B, C, D, or E.");
            }
            JOptionPane.showInputDialog(question);
        }
    }
}

Answer 1

你可以這樣做：

public static void main(String[] args) {

    Scanner scanner = new Scanner(System.in);

    String question = "What is the capital of Australia? \n"
            + "A. Sydney\n"
            + "B. Melbourne\n"
            + "C. Perth\n"
            + "D. Canberra\n"
            + "E. Brisbane\n";

    System.out.println(question);
    String answer = scanner.next().toUpperCase();

    while (true) {
        if (answer.equals("D")) {
            System.out.println("Correct");
            break;
        } else if (answer.equals("A") || answer.equals("B") || answer.equals("C") || answer.equals("E")) {
            System.out.println("Wrong answer, try again.");
        } else {
            System.out.println("Incorrect input");
        }
        answer = scanner.next().toUpperCase();
    }
}

我只使用控制台，沒有 JPannel，但你可以得到邏輯

結果控制台：

What is the capital of Australia? 
A. Sydney
B. Melburne
C. Perth
D. Cannberra
E. Brisbane

a
Wrong answer, try again.
b
Wrong answer, try again.
p
Incorrect input
d
Correct

---

要縮短檢查wearg 值，您可以使用：

String[] wrong = {"A", "B", "C", "E"};
...
Arrays.asList(wrong).contains(answer)

Answer 2

如果你在 while 開始的時候問答案，你只需要寫一次：

String answer =null;
while (true) {
    answer = scanner.next().toUpperCase();
    if (answer.equals("D")) {
        System.out.println("Correct");
        break;
    } else if (answer.equals("A") || answer.equals("B") || answer.equals("C") || answer.equals("E")) {
        System.out.println("Wrong answer, try again.");
    } else {
        System.out.println("Incorrect input");
    }
}

它也解決了你的錯誤:)