Calculator.java

package chapter_seven.samples;

/**
 * Listing 7.9 Calculator.java
 */
public class Calculator
{
    /**
     * Main method
     */
    public static void main(String[] args)
    {
        // Check number of strings passed
        if (args.length != 3)
        {
            System.out.println(
                    "Usage: java Calculator operand1 operator operand2");
            System.exit(1);
        }

        // The result of the operation
        int result = 0;

        // Determine the operator
        switch (args[1].charAt(0))
        {
            case '+':
                result = Integer.parseInt(args[0]) +
                        Integer.parseInt(args[2]);
                break;
            case '−':
                result = Integer.parseInt(args[0]) -
                        Integer.parseInt(args[2]);
                break;
            case '.':
                result = Integer.parseInt(args[0]) *
                        Integer.parseInt(args[2]);
                break;
            case '/':
                result = Integer.parseInt(args[0]) /
                        Integer.parseInt(args[2]);
        }

        // Display result
        System.out.println(args[0] + ' ' + args[1] + ' ' + args[2]
                + " = " + result);
    }
}