Why does my code skip straight to the else statement?

Question

Why does my code skip straight to the else statement? It returns the values inputted correctly if asked. But cant figure out why it just skips to "ERROR!" as opposed to proceeding to the relevant calculator. Here is my code:

package easy2;
import java.util.Scanner;
public class Calculator {

public static void main(String[] args) {

    float force, mass, acc;
    String answer = null;
    Scanner in = new Scanner(System.in);

    System.out.println("Force = Mass x Acceleration Calculator");

    System.out.println("Please state which variable you wish to work out: force, mass or acceleration");
    answer = in.nextLine();

    if(answer == "force"){      
        System.out.println("What is your mass in killograms?");
        mass = in.nextFloat();
        System.out.println("What is your acceleration in meters per second?");
        acc = in.nextFloat();

        force = mass * acc;

        System.out.println("The force of this equation in Netwon Meters is " + force);
        }
    else if(answer == "mass") {
            System.out.println("What is your force in Newton Meters?");
            force = in.nextFloat();
            System.out.println("What is your acceleration in meters per second?");
            acc = in.nextFloat();

            mass = force / acc;

            System.out.println("The mass of this equation is equal to " + mass + "kg");
    }
    else if(answer == "acceleration"){

        System.out.println("What is your force in Newton Meters?");
        force = in.nextFloat();
        System.out.println("What is your mass in killograms?");
        mass = in.nextFloat();

        acc = force / mass;

        System.out.println("The acceleration of this equation equals " + acc + "m/s");

    }
    else{System.out.println("ERROR!");
    }
}

}

Because you don't compare strings with `==` but with `.equals()`... — fge, Mar 19 '14 at 20:40
In Java you compare strings using string.equalsIgnoreCase(string); What you asked was whether the answer object and the string "force" were the same, which they are not. — ErstwhileIII, Mar 19 '14 at 20:42
Note .. questioner did not know that his question was about comparing strings, in all likelihood. — ErstwhileIII, Mar 19 '14 at 20:43
If it "jumps to the else", it means "the if(s) didn't succeed". Follow the yellow logic trail .. — user2864740, Mar 19 '14 at 20:44

PaulG · Answer 1 · 2014-03-19T20:44:48.847

2

Try using myString.equals("myOtherString"). You're doing the string comparison wrong.

== in Java is to compare objects for equality, not their values.

I've made the same mistake countless times.

edited Mar 19 '14 at 20:44

answered Mar 19 '14 at 20:42

PaulG

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Thanks that helped. New to coding and java, so didn't know about comparing strings. – SpruceMoose Mar 19 '14 at 23:20
I've been doing Java on and off for a good 4 years now, but I still forget. – PaulG Mar 20 '14 at 12:51

Why does my code skip straight to the else statement?

1 Answers1