YahooAnswersCalculator.java

import java.util.Scanner;

public class YahooAnswersCalculator {

    /*
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    */

    public static void main(String[] args) {
        // create scanner to read from keyboard
        Scanner in = new Scanner(System.in);
        char calculate, operator;
        double first=0.0, second=0.0, answer=0.0;

        System.out.print("Would you like to perform a calculation (y/n) ? ");
        calculate = in.nextLine().charAt(0);

        if (calculate=='n' || calculate=='N') System.exit(0);

        do {
            System.out.print("What type of calculation (+,-,*,/)? ");
            operator = in.nextLine().charAt(0);
        } while (operator!='+' && operator!='-' && operator!='*' && operator!='/');

        // input first, second numbers
        System.out.print("Enter first number: ");
        first = in.nextDouble();
        System.out.print("Enter second number: ");
        second = in.nextDouble();

        // perform correct calculation
        switch(operator) {
            case '+':   answer = first + second; break;
            case '-':   answer = first - second; break;
            case '*':   answer = first * second; break;
            case '/':   if (second==0) {
                        System.out.println("Division by zero error!");
                        System.exit(1);
                    } // if
                    answer = first / second;
            // no default required here
        } // switch

        // output result
        System.out.printf("%.3f %c %.3f = %.3f%n", first, operator, second, answer);
    } // main()
} // class