Check if 2 string are differents java

I have a problem with a if condition, I have this code :

if(!session.getAttribute("login").equals(d3.getLogin_demandeur())){
    //do something
}else{
    //do something else
}

So with this code if session.getAttribute("login") is equals to d3.getLogin_demandeur() it should go to the else statement, but this doesn't work, I have printed out these 2 values and they are the same and this still go to the else statement, any idea ?

EDIT :

Here is how I print

System.out.println(session.getAttribute("login")+"="+(d3.getLogin_demandeur()));

And what I have :

smilleto=smilleto