Thread: Very Basic Calculator

Hello all.

I'm a beginner in Java and I want to learn good programming habits.
I've made a basic calculator program and I was wondering if I could have done something different or shortened something in it, or even add anything to it.
The code works fine.

Any help is appreciated.

Thank you!

public class JavaApplication27 {
 
    static int numOne, numTwo;
 
    static Scanner scanStr = new Scanner(System.in);
    static String userInput;
    static String yesOrNo;
 
    public static void main(String[] args) {
        do {
            Scanner scanInt = new Scanner(System.in);
 
            System.out.println("Please enter your first number: ");
            numOne = scanInt.nextInt();
 
            System.out.println("Please enter your second number: ");
            numTwo = scanInt.nextInt();
 
            //Called the method inside the same class
            calculate();
            tryAgain();
 
        } while (yesOrNo.equals("Yes"));
    }
 
    public static void calculate() {
 
        do {
            System.out.println("What would you like to do with these numbers?");
            System.out.println("Input a function (+,-,*,/)");
 
            userInput = scanStr.next();
            switch (userInput) {
                case "+":
                    System.out.println("The answer is " + (numOne + numTwo));
                    break;
                case "-":
                    System.out.println("The answer is " + (numOne - numTwo));
                    break;
                case "*":
                    System.out.println("The answer is " + (numOne * numTwo));
                    break;
                case "/":
                    System.out.println("The answer is " + (numOne / numTwo));
                    break;
                default:
                    System.out.println("Invalid input");
                    break;
            }
        } while (!"+".equals(userInput) && !"-".equals(userInput)
                && !"*".equals(userInput) && !"/".equals(userInput));
 
    }
 
    public static void tryAgain() {
 
        do {
            System.out.println("Would you like to try again?");
            System.out.println("Input 'Yes' or 'No'");
 
            yesOrNo = scanStr.next();
 
            if (yesOrNo.equals("Yes")) {
                System.out.println("Okay!");
            }else if(yesOrNo.equals("No")){
                System.out.println("Thank you for using me!");
                System.exit(0);
            }
        } while (!"Yes".equals(yesOrNo));
    }
}

Good job! Sorry but no one is going to shorten it for you, and you shouldn't shorten it too.
This program has been made by you, and you only. This is your identity and changing this program for a shorter one made by someone else means changing your identity. There is nothing wrong in this program. It's good, and you should think that way too, because you made this. Not me, not the moderator, you. So you should be proud of it.

Still, if you want it shortened, do it yourself. Because you, are the programmer of this program. Again, good job and happy programming.

Originally Posted by Abhilash

Good job! ...

Still, if you want it shortened, do it yourself. Because you, are the programmer of this program. Again, good job and happy programming.

I appreciate your comment. I never thought of it that way. Coming into programming, I thought that there was a general way that people coded things. I don't want to do things the wrong way or did something that was considered bad coding practice. That's why I posted this in the first place.

You really helped [:

Thank.

Your code looks alright so far. For the size of the application that is.
Of course it would be nicer to have it use classes and polymorphism because that would make it easier to maintain and extend.

For example, what would you do if you wanted to add additional arithmetic operations? You would have to extend your switch-case statement and add additional cases.
What would be "nicer" in my personal opinion would be to add new "Operation" objects to an internal list of available operations.

Operations might look like this:

public interface ArithmeticOperation {
    public int calculate(int firstArg, int secondArg);
    public String getSymbol();
}

The Addition could then look like this:

public class Addition implements ArithmeticOperation {
    public int calculate(int firstArg, int secondArg) {
        return firstArg + secondArg;
    }
    public String getSymbol() {
        return "+";
    }
}

If you had several of these in a list you could then iterate over them and perform the right one depending on the user input and the "symbol" for the operation. For example:

List<ArithmeticOperation> operations = getSupportedOperations();
String input = scanStr.next();
boolean operationAvailable = false;
for (ArithmeticOperation op : operations) {
    if (op.getSymbol.equals(input) {
        int result = op.calculate(numOne, numTwo);
        // output result
        operationAvailable = true;
        break;
    }
}
if (!operationAvailable) {
    // tell user that operation is not available
}

Just a little suggestion.

The benefit of this would be that your calculator itself is completed and never needs to be rewritten when new operations are to be added. Instead you only have to create a new Operation-Object which implements the new operation; then add it to a list of supported operations.

Originally Posted by DreamHacked

I appreciate your comment. I never thought of it that way. Coming into programming, I thought that there was a general way that people coded things. I don't want to do things the wrong way or did something that was considered bad coding practice. That's why I posted this in the first place.

You really helped [:

Thank.

No problem. Just to add to your comment, there is no general way people code programs in java. And that's the fun of it, you can make programs the way you like. That's creates your identity as a programmer. Don't take anyone's suggestions, make programs your own way, the way you like.

Now, to make this clear, your program wasn't at all any type of "bad coding practice". Impression is another thing. Some might like your program, some would prefer taking input of operand (+,-,*,/) before input of numbers, while some would prefer the applet version of the program. Doesn't matter. What matters is efficiency and working, i.e. how fast you can make programs and whether your program works for different circumstances (Eg:- if user inputs letters for numbers, if user inputs brackets, etc. which you should not worry about right now). Keeping these in mind, make your programs well. I myself have unique ways of making programs. I usually make programs in such a way nobody understands how I do it, what logic I use, but it always helps me make programs much quicker than a normal student (See my success story for details, it is in member introductions). So, do it your way, do it well. Because your programs are your identity. And that's what defines you.

Thank you.

Well thank you. I'm really sorry but I didn't know the rules. Actually I was just giving DreamHacked advice regarding personal programming i.e. programming for projects, homework, etc. These rules apply for software engineers who make programs everyday and their programs need to be maintained and updated by others. I really didn't know the rules and I don't know about the others but it really did help me a lot. Although I'm just a student in a school but it will help me later in my life.

Thank you.

I have to bandwagon copeg here. Even tho Abhilash has a point in that each programmer has his/her own way of implementing things and one can often notice a certain style for each programmer, there definitely is conventions and so called "best practices" for programming in general and for each language in specific. And even on concept/task level ( for example best practices for socket programming in Java ). One can google for these and the result list is huge. Just remember to mirror the credentials of the writer to the claims - many of these articles have (probably) been written by people that don't really have the authority to give out best practices -advises ( e.g. Bjarne Stroustrup giving out tips on how to do stuff in C++ versus some newly graduated software engineer doing the same. You'd had to take the latter with a grain of salt. ).

I have enjoyed the Steve McConnell's Code Complete SE book Code Complete, Second Edition | Microsoft having a good amount of good practices for programming in general. As well as the Clean Code -book http://www.amazon.com/Clean-Code-Han.../dp/0132350882 by Robert C. Martin. But everyone has their own favourites, right?

Anyhow, your program seems fine to me for the scope of it, no worries . Shortness of program isn't always a virtue either, at least if the size doesn't add to performance too much.