字符不能转换为布尔值?
这是我做的第一个项目,我知道有很多错误。我试图用嵌套的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到boolean。我不知道为什么它认为我试图改变为布尔值,但我猜测“= A”等可能使它认为?任何建议将不胜感激。字符不能转换为布尔值?
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
}
}
}
char
不能转换到boolean
。
好像你想做检查。你可以这样做,
String sum = "0+3";
boolean isPlus = (sum.charAt(1) == '+');
isPlus
将现在指数自字符持有真正的sum
1“+”
或者他在'if'语句中使用赋值运算符。 –
@JonnyHenly是的。我在我的答案中也包括了,显示==如何生成布尔值 – 2016-03-03 05:14:33
如果块你分配到的结果。 你应该做的,如果(结果== 'A')// 'A' 不是一个
不正确。它应该是'A'。 –
你检查这样的:
if (result == 'A')
变化A
到'A'
和=
到==
为了要匹配字符,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多清晰度:
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 ");
}
}
}
感谢您的明确 – JOHNSMITH8338
当你写的
if(result = A)
它实际上是分配值A结果变量的条件。现在,因为A不是用引号引起来的,所以它假定A是一个变量,但由于它没有在程序中的任何地方声明,所以它假定它是一个布尔值。但结果的数据类型是char。因此它给你的数据类型不匹配错误。如果你把它写成
if(result == "A")
它会检查字母是否是A,错误将被删除。
赋值与平等。 ('='vs.'==')并且字符文字被单引号(''A'')包围。 –
更正:赋值表达式的类型是分配给变量的类型。所以表达式'aChar ='?''被键入为'char',但'if'只接受'布尔型'表达式。那么问题是“为什么不= =没有按预期的那样?”,其中有很多现有的教程/书籍/参考:) – user2864740