Java Equality

[anon538]

I am new to Java, and I am really confused by equality. Here is my current code:

String dm = JOptionPane.showInputDialog("Yes or no?");  
if(dm=="yes") 
{
   System.out.println("You chose yes.");
}
else
{
   System.out.println("You chose no.");
}

Even if I type in yes at the prompt, it always prints "You chose no". Is there something I don't understand about equality comparisons in Java? Please give me a modified version of my code that will work.

Thanks,
Anon

[JosAH]

I am new to Java, and I am really confused by equality. Even if I type in yes at the prompt, it always prints "You chose no". Is there something I don't understand about equality comparisons in Java? Please give me a modified version of my code that will work.

Thanks,
Anon

In Java all variables that are 'objects' (i.e. an instance of a class) are actually
just pointers to the real objects. Primitives such as ints, doubles etc. are stored
in the variable themselves.

Suppose you and I both point to a String "yes". Most likely I'm pointing to another
instance of a "yes" String than you are. Are we both pointing to the same
thing? I'd say no; that's exactly what the == operator does. It checks whether
or not both pointers are equal, i.e. if they point to the same thing.

What you want is to check whether or not those two separate things *represent*
the same thing. This ----> "yes" is another one than that ----> "yes", but they
both represent the same String wih content/value "yes".

Checking whether or not two different things represent the same value, you
should use the equals() method.

For primitives you can use the == operator again if you want to check them for
equality, e.g. 42 == 42 is true.

kind regards,

Jos

[anon538]

Thanks, it works perfectly.