Java while循环测试不'；t重置

作为我课程工作的一部分，我的任务是创建一个简单的问答游戏，循环直到用户选择正确的答案。 当答案正确（答案为B）或不正确时，我可以生成消息提示和响应提示，但我很难让while循环复位并再次提示用户。 目前，当用户得到错误的答案时，它会在响应提示上无限循环

import javax.swing.JOptionPane;
public class Quiz {      

public static void main(String[] args) {
    String question =  "What colour is the sky?\n";
     question += "A. Purple\n";
     question += "B. Blue\n";
     question += "C. Green\n";
     question += "D. Yellow\n";
     question += "E. Orange\n";

     String answer = JOptionPane.showInputDialog(question);
     answer = answer.toUpperCase();

     int guess = 0;
     while (answer != "B")

     if (answer.equals("B")) {
         JOptionPane.showMessageDialog(null,"Correct!");
         break;
        }
     else if (answer.equals("A")) {
         JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
        }
     else if (answer.equals("C")) {
         JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
        }
     else if (answer.equals("D")) {
         JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
        }
     else if (answer.equals("E")) {
         JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
        }
     else {
         JOptionPane.showMessageDialog(null, "Invalid answer. Please enter A, B, C, D, or E.");
        }
     guess++;
}
}

而不是

while (answer != "B"){

         answer = JOptionPane.showInputDialog(question);
         answer = answer.toUpperCase();

         if (answer.equals("B")) {
             JOptionPane.showMessageDialog(null,"Correct!");
             break;
            }
         else if (answer.equals("A")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else if (answer.equals("C")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else if (answer.equals("D")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else if (answer.equals("E")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else {
             JOptionPane.showMessageDialog(null, "Invalid answer. Please enter A, B, C, D, or E.");
            }
         guess++;
}

你错过了大括号。

而不是

while (answer != "B"){

         answer = JOptionPane.showInputDialog(question);
         answer = answer.toUpperCase();

         if (answer.equals("B")) {
             JOptionPane.showMessageDialog(null,"Correct!");
             break;
            }
         else if (answer.equals("A")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else if (answer.equals("C")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else if (answer.equals("D")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else if (answer.equals("E")) {
             JOptionPane.showMessageDialog(null,"Incorrect. Please try again!");
            }
         else {
             JOptionPane.showMessageDialog(null, "Invalid answer. Please enter A, B, C, D, or E.");
            }
         guess++;
}

---

你错过了大括号。

你忘了再给一次回答问题的机会。 现在它正按照你的预期工作

    public static void main(String[] args) {
    String question =  "What is the Capital of South Africa?\n";
    question += "A. Cape town\n";
    question += "B. Pretoria\n";
    question += "C. Johannesburg\n";
    question += "D. Durban\n";
    question += "E. Nelspruit\n";

    String answer = JOptionPane.showInputDialog(question);
    answer = answer.toUpperCase();

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

---

你忘了再给一次机会回答这个问题。 现在它正按照你的预期工作

    public static void main(String[] args) {
    String question =  "What is the Capital of South Africa?\n";
    question += "A. Cape town\n";
    question += "B. Pretoria\n";
    question += "C. Johannesburg\n";
    question += "D. Durban\n";
    question += "E. Nelspruit\n";

    String answer = JOptionPane.showInputDialog(question);
    answer = answer.toUpperCase();

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

---

如果用户输入不是

B

，则必须反复提示问题。在while循环中，您需要更改变量

answer

的值。尝试下面的工作片段

public class Quiz{

    public static void main(String[] args) throws IOException {

        String answer = promptQuestion();

        while (answer != "B") {
            if (answer.equals("B")) {
                JOptionPane.showMessageDialog(null, "Correct!");
                break;
            } else if (answer.equals("A")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else if (answer.equals("C")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else if (answer.equals("D")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else if (answer.equals("E")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else {
                JOptionPane.showMessageDialog(null, "Invalid answer. Please enter A, B, C, D, or E.");
                answer = promptQuestion();
            }
        }
    }

    public static String promptQuestion() {
        String question = "What is the Capital of South Africa?\n";
        question += "A. Cape town\n";
        question += "B. Pretoria\n";
        question += "C. Johannesburg\n";
        question += "D. Durban\n";
        question += "E. Nelspruit\n";

        String answer = JOptionPane.showInputDialog(question);
        return answer.toUpperCase();
    }

}

---

如果用户输入不是

B

，则必须反复提示问题。在while循环中，您需要更改变量

answer

的值。尝试下面的工作片段

public class Quiz{

    public static void main(String[] args) throws IOException {

        String answer = promptQuestion();

        while (answer != "B") {
            if (answer.equals("B")) {
                JOptionPane.showMessageDialog(null, "Correct!");
                break;
            } else if (answer.equals("A")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else if (answer.equals("C")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else if (answer.equals("D")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else if (answer.equals("E")) {
                JOptionPane.showMessageDialog(null, "Incorrect. Please try again!");
                answer = promptQuestion();
            } else {
                JOptionPane.showMessageDialog(null, "Invalid answer. Please enter A, B, C, D, or E.");
                answer = promptQuestion();
            }
        }
    }

    public static String promptQuestion() {
        String question = "What is the Capital of South Africa?\n";
        question += "A. Cape town\n";
        question += "B. Pretoria\n";
        question += "C. Johannesburg\n";
        question += "D. Durban\n";
        question += "E. Nelspruit\n";

        String answer = JOptionPane.showInputDialog(question);
        return answer.toUpperCase();
    }

}

---

guess++不是while

循环的一部分，仅供参考。还有

while（answer！=“B”）

和

if（answer.equals（“B”）

这些语句是相互矛盾的。在while循环中，使用括号（

{…}

）作为循环。在while循环中，您永远不会更改变量

answer

的值。因此循环要么根本不运行，要么无限次运行。如果用

equals

检查相等，为什么用

检查不相等=？看看
guess++不是while
循环的一部分，仅供参考。还有
while（answer！=“B”）
和
if（answer.equals（“B”）
这些语句是相互矛盾的。在while循环中，使用括号（
{…}
）作为循环。在while循环中，您永远不会更改变量
answer
的值。因此循环要么根本不运行，要么无限次运行。如果用
equals
检查相等，为什么用
检查不相等=？看一看，而不是什么？另外，如果你指的是大括号，那不是唯一的问题。
while（答案！=“B”）
应该是
while（“B”。equals（答案））
@karthikeyanvaitillingam哦，我想你是对的！字符串值必须使用等于函数。而不是什么？另外，如果你指的是大括号，那不是唯一的问题。
while（答案！=“B”）
应该是
while（“B”。equals（答案））
@karthikeyanvaitillingam哦，我想你是对的！字符串值必须使用equals函数。一些建议将
answer=JOptionPane.showInputDialog（问题）；answer=answer.toUpperCase（）在while循环的末尾也
while（答案！=“B”）
应该是
while（“B”.equals（答案））
一些建议将
answer=JOptionPane.showInputDialog（问题）；answer=answer.toUpperCase（）也
while（答案！=“B”）
应该是
while（“B”。等于（答案））