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Thread: A basic calculator

  1. #1
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    Default A basic calculator

    Hey, I'm new to java, and I'm trying to make a calculator, with the choice of + or -. My code is:

    import java.util.Scanner;
    public class Funk {
    public static void main (String[] args) {
     
    	double first;
    	double second;
    	String plussminus;
    	double sum = 0;
    	Scanner input = new Scanner (System.in);
    	Scanner pm = new Scanner (System.in);
    	System.out.print("First number: ");
    	first = input.nextDouble();
     
    System.out.print("+ or -? ");
    plussminus = pm.nextLine();
     
     
     
    	System.out.print("Second number: ");
    	second = input.nextDouble();
     
    	if (plussminus == "plus") {
    	sum = first + second; }
    	else if (plussminus == "minus") {
    	sum = first - second; }
    	else {
    		System.out.println("You did something wrong.");}
     
    	System.out.println(sum);
     
     
    }
    }

    But it always says "You did something wrong.", and i get the answer "0.0". I've tried for quite some time now, but can't get it to work.


  2. #2
    Crazy Cat Lady KevinWorkman's Avatar
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    Default Re: A basic calculator

    Don't use == to test String equality. Use the equals() method instead. The first tests whether they are the same instance, the second tests whether they are semantically equivalent.
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  3. #3
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    Default Re: A basic calculator

    Quote Originally Posted by KevinWorkman View Post
    Don't use == to test String equality. Use the equals() method instead. The first tests whether they are the same instance, the second tests whether they are semantically equivalent.
    Thank you! This is the first time i have ever heard of that method at all, so I just learned something new! And thank you for a fast reply

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