java - 如何在计算中使用用户输入的字符？

Question

如何接受符号(*、+ 或 -)并在 Java 中进行计算？示例:

int n = 10;
int f = 10;
//sign is the user input for the character to be used in the calculation.

/* Insert something along the lines of int r = f sign n;
   if sign is equal to '-', then the result should be 0, 
   if sign is '+', result should be 20. 
   etc. */

Answer 1

您可以使用java.util.Scanner类来读取用户的输入，然后使用 if..else if.. else 条件或 switch 语句来执行算术。

Scanner scanner = new Scanner(System.in);
String operator = scanner.nextLine();
switch (operator) {
  case "+":
    r = f + n;
    break;
  case "-": 
    r = f - n;
    break;
  case "*":
    r = f * n;
    break;
  case "/":
    r = f / n;
    break;
  default:
    throw new IllegalArgumentException("Unknown operators.");
}