# Java 程序：使用`Switch Case`制作計算器 > 原文： [https://beginnersbook.com/2017/09/java-program-to-make-a-calculator-using-switch-case/](https://beginnersbook.com/2017/09/java-program-to-make-a-calculator-using-switch-case/) 在本程序中，我們正在制作一個簡單的計算器，根據用戶輸入執行加法，減法，乘法和除法。程序獲取兩個數字的值（由用戶輸入），然后要求用戶輸入操作（`+`，`-`，`*`和`/`），根據輸入程序使用[對輸入的數字執行所選操作`switch-case`](https://beginnersbook.com/2017/08/java-switch-case/)。 > 如果您是 java 新手，請參閱 [Java 教程](https://beginnersbook.com/java-tutorial-for-beginners-with-examples/)，從基礎開始學習 java 編程。 ## 示例：使用的`switch case`編寫計算器的程序 ```java import java.util.Scanner; public class JavaExample { public static void main(String[] args) { double num1, num2; Scanner scanner = new Scanner(System.in); System.out.print("Enter first number:"); /* We are using data type double so that user * can enter integer as well as floating point * value */ num1 = scanner.nextDouble(); System.out.print("Enter second number:"); num2 = scanner.nextDouble(); System.out.print("Enter an operator (+, -, *, /): "); char operator = scanner.next().charAt(0); scanner.close(); double output; switch(operator) { case '+': output = num1 + num2; break; case '-': output = num1 - num2; break; case '*': output = num1 * num2; break; case '/': output = num1 / num2; break; /* If user enters any other operator or char apart from * +, -, * and /, then display an error message to user * */ default: System.out.printf("You have entered wrong operator"); return; } System.out.println(num1+" "+operator+" "+num2+": "+output); } } ``` 輸出： ```java Enter first number:40 Enter second number:4 Enter an operator (+, -, *, /): / 40.0 / 4.0: 10.0 ```