Basic java calculator,Won't give any output

Question

Ok so I'm teaching myself (along with the help of some youtube videos) java. So after a few videos I thought I would try and test my skills by setting up a calculator. now I had done this before with lua but its a somewhat diffrent ball game here. my issue is that no matter how i set up any variables or if/else statements, the program always ends up just skipping over the else ifs. i put a final else at the base of the code to see if it was even reaching the bottom and it was definitly, so heres my code

import java.util.Scanner;


public class calculator {
public static void main(String[] args){
    double Answer;
    String op;
    double num1;
    double num2;

    Scanner input = new Scanner(System.in);

    System.out.print("What opperation would you like to preform? +,-,*,/, :");
    op = input.nextLine();


    System.out.print("What is the first number? : ");
    num1 = input.nextDouble();

    System.out.print("And the seccond number? : ");
    num2 = input.nextDouble();


    if(op == "+"){
        Answer = (num1 + num2);
        System.out.print(Answer);

    }else if(op == "-"){
        Answer = num1 - num2;
        System.out.print(Answer);

    }else if(op == "*"){
        Answer = num1 * num2;
        System.out.print(Answer);

    }else if(op == "/"){
        Answer = num1 / num2;
        System.out.print(Answer);

    }else{
        System.out.print("ilikecake");
    }

}

}

as you can see, i used a string for the opperation (op) variable due to the flexability of strings in this particular application, also, i couldn't figure out how to get scanner to accept a char variable. i keep getting the string can not be converted to char error so i just set it up as a string. if you can help thank you! also please ignore any akward formatting from the post, i couldn't figure out how to make the code appear properly so i did my best :/

Not a java programmer, but check this out: http://stackoverflow.com/questions/767372/java-string-equals-versus — Gray, Jul 25 '13 at 20:00
Compare String values with String's `equals` method, which compares string contents, not with `==`, which compares two objects to see if they are the same object. — rgettman, Jul 25 '13 at 20:00
Also use lowercase variable names in Java (Answer -> answer). Capitalized names are used only for classes and interfaces. — Ma3x, Jul 25 '13 at 20:03

score 5 · Answer 1 · edited May 23 '17 at 11:49

5

Use the

.equals()

method for comparing strings. The == operator tests for equal references, and you want to check for equivalent values.

Read more here: How do I compare strings in Java?

edited May 23 '17 at 11:49

Community

1
1

answered Jul 25 '13 at 20:01

Undefined

655
1
4
13

the .equals() worked. thanks again guys! looks like im going to have to do some API research >_> lol – user2620255 Jul 25 '13 at 20:15

score 2 · Answer 2 · edited May 23 '17 at 12:13

2

Do NOT compare Strings with ==. To compare Strings, use the .equals() method., aka: if (op.equals("+"))

In short, == compares references, whereas .equals() actually compares the the contents (values) of the Strings. I would go into more detail, but it has been covered in many threads, for example.

edited May 23 '17 at 12:13

Community

1
1

answered Jul 25 '13 at 20:01

Steve P.

14,489
8
42
72

wow this is an amazing community thanks ppls :D i appreciate the help so much! – user2620255 Jul 25 '13 at 20:13
@user2620255 No problem. Welcome to SO. Here, take the [tour](http://stackoverflow.com/about). – Steve P. Jul 25 '13 at 20:15

Basic java calculator,Won't give any output

2 Answers2