Question

这是我做的第一个项目，所以我知道有很多错误。我正在尝试使用嵌套的if else语句创建一个计算器。我得到的唯一错误是在if语句中我得到的是我不能从char转到boolean。我不知道为什么它认为我试图改为布尔但我'，猜猜“= A”等可能让它认为呢？任何建议将不胜感激。

public static void main(String[] args) { //main class
    char result = 0; //define and declare variables
    double firstNumber = 0;
    double secondNumber = 0;
    double answer = 0;

    System.out.println("Calculator Program\n"); //Text for user
    System.out.println("Choose how to proceed:\n");
    System.out.println("A. Add\n");
    System.out.println("B. Subtract\n");
    System.out.println("C. Multiply\n");
    System.out.println("D. Divide\n");

    Scanner userInput = new Scanner(System.in); //create new Scanner
    result = userInput.next().charAt(0); //Take only the first letter entered

    if (result = A){

        System.out.println("Please enter the first number: ");
            firstNumber = userInput.nextDouble(); //redefine first number
                userInput.next(); //clears line
        System.out.println("Please enter the second number: ");
            secondNumber = userInput.nextDouble(); //redefine second number 
                userInput.next(); //clears line

        answer = firstNumber + secondNumber; //algorithim 
        System.out.println("Answer: " + firstNumber + " + " + secondNumber + " = " + answer);//print answer

                   }

            else if ( result = B){
                   System.out.println("Please enter the first number: ");
                    firstNumber = userInput.nextDouble(); //redefine first number
                        userInput.next(); //clears line
                System.out.println("Please enter the second number: ");
                    secondNumber = userInput.nextDouble(); //redefine second number 
                        userInput.next(); //clears line

                answer = firstNumber - secondNumber; //algorithim 
                System.out.println("Answer: " + firstNumber + " - " + secondNumber + " = " + answer);//print answer

                                }

                    else if ( result = C){
                          System.out.println("Please enter the first number: ");
                           firstNumber = userInput.nextDouble(); //redefine first number
                               userInput.next(); //clears line
                       System.out.println("Please enter the second number: ");
                           secondNumber = userInput.nextDouble(); //redefine second number 
                               userInput.next(); //clears line

                       answer = firstNumber * secondNumber; //algorithim 
                       System.out.println("Answer: " + firstNumber + " * " + secondNumber + " = " + answer);//print answer
                                           }

                            else if ( result = D){
                              System.out.println("Please enter the first number: ");
                             firstNumber = userInput.nextDouble(); //redefine first number
                                 userInput.next(); //clears line
                         System.out.println("Please enter the second number: ");
                             secondNumber = userInput.nextDouble(); //redefine second number 
                                 userInput.next(); //clears line

                         answer = firstNumber / secondNumber; //algorithim 
                         System.out.println("Answer: " + firstNumber + " / " + secondNumber + " = " + answer);//print answer 
                                      }



}

}

Answer 1

char无法转换为boolean。

好像你想要检查一下。你可以做点什么，

String sum = "0+3";

boolean isPlus = (sum.charAt(1) == '+');

isPlus现在将成立，因为sum的索引1处的字符为'+'

Answer 2

在if块中，您将A分配给结果。你应该这样做（结果==＆＃39; A＆＃39;）//＆＃39; A＆＃39;不是A

Answer 3

你这样检查：

if (result == 'A')

将A更改为'A'，将=更改为==

Answer 4

为了匹配字符，您需要将if语句更改为if（result =='A'）而不是if（result == A）

以下代码将为您提供更清晰的信息：

    import java.util.Scanner;
public class checkBoolToChar {
    public static void main(String[] args) {
        char a  = 0;
        Scanner in = new Scanner(System.in);
        a = in.next().charAt(0);

        if(a ==  'A'){
            System.out.println("Match ");
        }
    }
}

Answer 5

当您将条件写为

时

    if(result = A)

它实际上是将值A分配给结果变量。现在，由于A不是用引号编写的，它假设A是一个变量，但由于它没有在程序中的任何地方声明，因此它假定它是一个布尔值。但结果的数据类型是char。因此它会为您提供数据类型不匹配错误。如果你把它写成

    if(result == "A")

它将检查字母是否为A并且错误将被删除。

char无法转换为布尔值？

5 个答案: