Why don't these two variables equal each other?

Question

I'm trying to identify an object based on user input and have no idea why it's not working...

userInput is just a scanner, and allGames is an arraylist of a bunch of 'Game' classes with IDs like S01, S02 etc.

Game gameToChange = null;
for (Game g : allGames){
        System.out.println(g.getId());
}
String gameInput = userInput.nextLine();
    System.out.println(gameInput);
    for (Game g : allGames){
        if (gameInput == g.getId()){
            System.out.println("Found it");
            gameToChange =g;
        }
    }

The Game class:

public abstract class Game {

    private String identifier;

    public Game(String id){
        identifier = id;
    }

    public String getId(){
        return this.identifier;
    }
}

I have the printout for "found it" just so I can check when it's working...but no matter when I enter the correct string, one that matches one which is already printed out, it never equals it.

`String` comparison in Java is done using `String@equals` not `==`, the difference between comparing the contents of the `String` and the memory location of two different instances of `String`... — MadProgrammer, Sep 22 '14 at 06:11

score 1 · Answer 1 · answered Sep 22 '14 at 06:10

1

Since these two gameInput and g.getId() are type Strings.

You should use equals() instead of ==

equals() compare the content each variable

== compare the reference if they are looking at the same thing or not

answered Sep 22 '14 at 06:10

Kick Buttowski

6,709
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score 1 · Accepted Answer · answered Sep 22 '14 at 06:11

1

Change

if (gameInput == g.getId()){

to

if (gameInput != null && gameInput.equals(g.getId())){

answered Sep 22 '14 at 06:11

ROMANIA_engineer

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Ahhhhhh thanks, I get caught up in looking for bigger problems and forget about things like this. Appreciate it. – Jordan Andrews Sep 22 '14 at 06:14
@JordanAndrews did you understand why? – Kick Buttowski Sep 22 '14 at 06:15
1

I believe I was testing whether it was actually the same object, not whether the two strings were actually the same – Jordan Andrews Sep 22 '14 at 06:17

Why don't these two variables equal each other?

2 Answers2