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Thread: Need help with creating simple calculater

  1. #1
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    Default Need help with creating simple calculater

    Hey,

    I made myself a small calculator, but I want to to choose what to use instead of only using plus.

    import java.util.Scanner;
     
    class calculator{
    	public static void main(String args[]){
    		Scanner thingy = new Scanner(System.in);
    		double firstnumber, secondnumber, answer;
     
    		System.out.println("Enter first number:");
    		firstnumber = thingy.nextDouble();			
    		System.out.println("Enter second number");
    		secondnumber = thingy.nextDouble();
    		answer = firstnumber + secondnumber;
    		System.out.println(answer);
    	}
    }

    What do I need to write in order to make it?


  2. #2
    Super Moderator Norm's Avatar
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    Default Re: Need help with creating simple calculater

    You need to decide what you want the code to do, what steps are needed and write the java code that will do those steps. Do you know what steps you want the code to do?

  3. #3
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    Default Re: Need help with creating simple calculater

    import java.util.Scanner;

    class epler{
    public static void main(String args[]){
    Scanner scn = new Scanner(System.in);
    double firstnumber, secondnumber, answer;

    //Need a declaration for my mode, not sure which.


    System.out.println("Enter first number: ");
    firstnumber = scn.nextDouble();

    System.out.println("Enter method: ");
    mode = scn.nextInt();
    if(mode == '+'){
    System.out.println("Enter second number: ");
    secondnumber = scn.nextDouble();

    answer = firstnumber + secondnumber;
    System.out.println(answer);
    }else if(mode == '-'){
    System.out.println("Enter second number: ");
    secondnumber = scn.nextDouble();

    answer = firstnumber - secondnumber;
    System.out.println(answer);
    }else if(mode == '*'){
    System.out.println("Enter second number: ");
    secondnumber = scn.nextDouble();

    answer = firstnumber * secondnumber;
    System.out.println(answer);
    }else if(mode == '/'){
    System.out.println("Enter second number: ");
    secondnumber = scn.nextDouble();

    answer = firstnumber / secondnumber;
    System.out.println(answer);
    }

    }
    }
    This is what I've gotten to, but I need a declaration for my mode variable. Anyone knows what kind?

  4. #4
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    Default Re: Need help with creating simple calculater

    What type of data are you going to store in the mode variable?
    That would determine how you define it.

  5. #5
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    Default Re: Need help with creating simple calculater

    The mode would be for the method user input. What is written in the input in "Enter method: ", will determine if you are going to +, -, * or /.

  6. #6
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    Default Re: Need help with creating simple calculater

    Do you want mode to hold a String or a char value? "+' or '+'

  7. #7
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    Default Re: Need help with creating simple calculater

    Not quite sure. I'm here cause I need some help finishing this one. How would you have done it?

  8. #8
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    Default Re: Need help with creating simple calculater

    The Scanner class has a method for reading a String, so that might be easier.

  9. #9
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    Default Re: Need help with creating simple calculater

    I'm not really into Strings. How do I use them?

  10. #10
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    Default Re: Need help with creating simple calculater

    Take a look at the API doc for String class and its methods:
    Java Platform SE 6
    Find String in the lower left, click on it and the doc will display in the main window.

    Also look at the doc for the Scanner class for samples.

  11. #11
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    Default Re: Need help with creating simple calculater

    I added a string above: String str;

    But now, at
    if(str == '+'){
    I get "Incompatible operand types String and char"
    Why is that?

    If I change it to

    if(str = +){
    the + sign gets an error.

  12. #12
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    Default Re: Need help with creating simple calculater

    To compare Strings, you need to use the equals() method:
    str.equals("+")

    I get "Incompatible operand types String and char"
    Why is that?
    String and char are not compatible. String is an object, char is a primitive.

  13. The Following User Says Thank You to Norm For This Useful Post:

    YourCrazyFriend (March 2nd, 2012)

  14. #13
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    Default Re: Need help with creating simple calculater

    I fixed it Thank you so much

  15. #14
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    Default Re: Need help with creating simple calculater

    You're welcome.

  16. #15
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    Default Re: Need help with creating simple calculater

    Ended up with making this:

    import java.util.Scanner;
     
    class apples{
    	public static void main(String args[]){
    		Scanner scn =  new Scanner(System.in);
    		double firstnumber, secondnumber, answer;
    		String str;
     
    		System.out.println("Enter first number: ");
    		firstnumber = scn.nextDouble();
     
    		System.out.println("Enter method: ");
    		str = scn.next();
     
    		if(str.equals("+")){
    			System.out.println("Enter second number: ");
    			secondnumber = scn.nextDouble();
     
    			answer = firstnumber + secondnumber;
    			System.out.println(firstnumber + " plus " + secondnumber + " equals " + answer);
     
    			}else if(str.equals("-")){
    				System.out.println("Enter second number: ");
    				secondnumber = scn.nextDouble();
     
    				answer = firstnumber - secondnumber;
    				System.out.println(firstnumber + " minus " + secondnumber + " equals " + answer);
     
    			}else if(str.equals("*")){
    				System.out.println("Enter second number: ");
    				secondnumber = scn.nextDouble();
     
    				answer = firstnumber * secondnumber;
    				System.out.println(firstnumber + " multiplied with " + secondnumber + " equals " + answer);
     
    			}else if(str.equals("/")){
    				System.out.println("Enter second number: ");
    				secondnumber = scn.nextDouble();
     
    				answer = firstnumber / secondnumber;
    				System.out.println(firstnumber + " divided by " + secondnumber + " equals " + answer);
     
    			}else if(str.equals(":")){
    				System.out.println("Enter second number: ");
    				secondnumber = scn.nextDouble();
     
    				answer = firstnumber / secondnumber;
    				System.out.println(firstnumber + " divided by " + secondnumber + " equals " + answer);
     
    			}else if(str.equals("%")){
    				System.out.println("Enter second number: ");
    				secondnumber = scn.nextDouble();
     
    				answer = firstnumber % secondnumber;
    				System.out.println("The leftovers from dividing " + firstnumber + " by " + secondnumber + " equals " + answer);
     
    			}else if(str.equals("sqrt")){
    				answer = Math.pow(firstnumber, 0.5);
    				System.out.println("The squareroot of " + firstnumber + " equals " + answer);
     
    			}else if(str.equals("squareroot")){
    				answer = Math.pow(firstnumber, 0.5);
    				System.out.println("The squareroot of " + firstnumber + " equals " + answer);
     
    			}else if(str.equals("^")){
    				System.out.println("Enter second number: ");
    				secondnumber = scn.nextDouble();
     
    				answer = Math.pow(firstnumber, secondnumber);
    				System.out.println(firstnumber + " ^ " + secondnumber + " equals " + answer);
     
    			}else{
    				System.out.println("Error, please try another method.");
    			}
    	}
    }
    Last edited by YourCrazyFriend; March 2nd, 2012 at 09:22 AM.

  17. #16
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    Default Re: Need help with creating simple calculater

    Your posted code would be easier to read if you used code tags.
    [code] ...[/code]

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