Java 程序：使用 switch...case 创建简单计算器

示例：使用Java switch语句的简单计算器

import java.util.Scanner;

class Main {
  public static void main(String[] args) {

    char operator;
    Double number1, number2, result;

    // create an object of Scanner class
    Scanner input = new Scanner(System.in);

    // ask users to enter operator
    System.out.println("Choose an operator: +, -, *, or /");
    operator = input.next().charAt(0);

    // ask users to enter numbers
    System.out.println("Enter first number");
    number1 = input.nextDouble();

    System.out.println("Enter second number");
    number2 = input.nextDouble();

    switch (operator) {

      // performs addition between numbers
      case '+':
        result = number1 + number2;
        System.out.println(number1 + " + " + number2 + " = " + result);
        break;

      // performs subtraction between numbers
      case '-':
        result = number1 - number2;
        System.out.println(number1 + " - " + number2 + " = " + result);
        break;

      // performs multiplication between numbers
      case '*':
        result = number1 * number2;
        System.out.println(number1 + " * " + number2 + " = " + result);
        break;

      // performs division between numbers
      case '/':
        result = number1 / number2;
        System.out.println(number1 + " / " + number2 + " = " + result);
        break;

      default:
        System.out.println("Invalid operator!");
        break;
    }

    input.close();
  }
}

输出 1

Choose an operator: +, -, *, or /
*
Enter first number
3
Enter second number
9
3.0 * 9.0 = 27.

在这里，我们使用Scanner类从用户那里获取3个输入。

• 运算符 - 指定要执行的操作
• number1/number2 - 用于执行操作的操作数

由于运算符与case '*'匹配，因此将执行相应的代码。

result = number1 * number2;
System.out.println(number + " * " + number2 + " = " + result);
break;

这些语句计算两个数字的乘积并打印输出。最后，break语句结束switch语句。

同样，对于不同的运算符，将执行不同的case。

输出 2

Choose an operator: +, -, *, or /
+
Enter first number
21
Enter second number
8
21.0 + 8.0 = 29.0

输出 3

Choose an operator: +, -, *, or /
-
Enter first number
9
Enter second number
3
9.0 - 3.0 = 6.0

输出 4

Choose an operator: +, -, *, or /
/
Enter first number
24
Enter second number
8
24.0 / 8.0 = 3.0