Java 扫描器和用户输入文本框

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已关闭。这个问题是 not reproducible or was caused by typos 。目前不接受答案。

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这个问题是由拼写错误或无法再重现的问题引起的。虽然类似的问题可能是 on-topic在这里，这个问题的解决方式不太可能帮助 future 的读者。

已关闭 8 年前。

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我在 BlueJ IDE 中使用 Java 代码时遇到了一些问题。我想做的是问用户:“1 x 3 是什么？”并有一个文本框，用户可以在其中输入答案，然后按按钮提交答案。如果答案正确，程序将显示一条消息“正确”，如果答案错误，则显示“不正确，请重试”。这是我编写的代码:

Scanner input = new Scanner(System.in);
    //prompt the user to enter thier answer to the question
//create two labels to explain input 

double answer = 3; //the correct answer to the multiplication question

   JLabel labelAnswer =  new JLabel("What is 1 x 3?"); //ask user this
   double userAnswer = input.nextDouble();
   //prompt the user to enter the gallons
   if (userAnswer = 3) //if the user enters 3 into the text box, a message will be displayed saying: Correct!{
     { if (userAnswer == 3) 
      {System.out.println("Correct!");  

      break;
    }
    if (userAnswer != 3) //if the user enters anything others than 3, it is incorrect
    {
        System.out.println("Incorrect, Please try again!"); 

    }

我收到的错误代码表明 double 值无法转换为 boolean 值。我该如何解决这个问题？谢谢

Answer 1

你必须解决这个问题:

if(userAnswer = 3)

将其更改为:

if(userAnswer == 3)

我还可以推荐这个以节省空间吗？

if(userAnswer == 3)
    System.out.println("Correct!");
else
    System.out.println("Incorrect, Please try again!");

而不是:

if (userAnswer = 3) //if the user enters 3 into the text box, a message will be displayed saying: Correct!{
     { if (userAnswer == 3) 
      {System.out.println("Correct!");  

      break;
    }
    if (userAnswer != 3) //if the user enters anything others than 3, it is incorrect
    {
        System.out.println("Incorrect, Please try again!"); 

    }

此外，您调用 break，但您永远不会进入可以中断的循环。