Java 编写简单计算器程序

使用 switch 语句和 else if 语句编写一个简单的 Java 计算器程序。第一个示例允许输入两个数值和要执行的运算符。

接下来，我们使用 switch 语句根据给定的运算符执行计算。例如，如果我们输入 +，switch 语句将执行加法。在这里，我们还使用 default 语句处理错误的运算符，以通知用户输入错误。

package SimpleNumberPrograms;
import java.util.Scanner;
public class Calculator {
	private static Scanner sc;
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		double a, b, result;	
		System.out.print("Please Enter any Two Numbers = ");
		a = sc.nextDouble();
		b = sc.nextDouble();	
		System.out.print("Enter any Operator from +, - , /, *, % = ");
		char operator = sc.next().charAt(0);	
		switch(operator) {
		case '+':
			result = a + b;
			break;
		case '-':
			result = a - b;
			break;
		case '*':
			result = a * b;
			break;
		case '/':
			result = a / b;
			break;
		case '%':
			result = a % b;
			break;
		default:
			System.out.println("You have entered incorrect operator");
			return;
		}		
		System.out.printf("%.2f %c %.2f = %.2f", a, operator, b, result);
	}
}

让我输入一个错误的符号。

Please Enter any Two Numbers = 11 4
Enter any Operator from +, - , /, *, % = #
You have entered incorrect operator

使用 else if 编写 Java 计算器程序

在这个示例中，我们用else if 条件替换了 switch 语句，以创建一个简单的计算器。

package SimpleNumberPrograms;
import java.util.Scanner;
public class Example2 {

	private static Scanner sc;
	public static void main(String[] args) {
		sc = new Scanner(System.in);
		double a, b, result = 0;
		
		System.out.print("Please Enter any Two Numbers = ");
		a = sc.nextDouble();
		b = sc.nextDouble();
		
		System.out.print("Enter any Operator from +, - , /, *, % = ");
		char operator = sc.next().charAt(0);
		
		if(operator == '+') {
			result = a + b;
		}
		else if(operator == '-') {
			result = a - b;
		}
		else if(operator == '*') {
			result = a * b;
		}
		else if(operator == '/') {
			result = a / b;
		}
		else if(operator == '%') {
			result = a % b;
		}
		else {
			System.out.println("You have entered incorrect operator");
		}
		
		System.out.printf("%.2f %c %.2f = %.2f", a, operator, b, result);
	}
}

Please Enter any Two Numbers = 20 32
Enter any Operator from +, - , /, *, % = -
20.00 - 32.00 = -12.00

这个简单的计算器程序与上面的示例相同。但是，我们为每个计算创建了一个单独的函数。在实际应用中，最好创建一个包含这些方法的独立类，并创建该类的一个实例以便在主程序中调用它们。

import java.util.Scanner;

public class Example {
	private static Scanner sc;

	public static void main(String[] xrgs) {
		sc = new Scanner(System.in);
		double x, y, result = 0;

		System.out.print("Enter Two Numbers = ");
		x = sc.nextDouble();
		y = sc.nextDouble();

		System.out.print("Enter anyy opt from +, - , /, *, % = ");
		char opt = sc.next().charAt(0);

		if (opt == '+') {
			result = add(x, y);
		} else if (opt == '-') {
			result = sub(x, y);
		} else if (opt == '*') {
			result = mul(x, y);
		} else if (opt == '/') {
			result = div(x, y);
		} else if (opt == '%') {
			result = mod(x, y);
		} else {
			System.out.println("You have entered incorrect option");
		}

		System.out.printf("%.2f %c %.2f = %.2f", x, opt, y, result);
	}

	static double add(double x, double y) {
		return x + y;
	}

	static double sub(double x, double y) {
		return x - y;
	}

	static double mul(double x, double y) {
		return x * y;
	}

	static double div(double x, double y) {
		return x / y;
	}

	static double mod(double x, double y) {
		return x % y;
	}

}

Enter Two Numbers = 22
8
Enter anyy opt from +, - , /, *, % = %
22.00 % 8.00 = 6.00