Thread: out of range help.

I am having a problem. When i input "na" into the textfield it should output na but instead what its doing is giving me a out of range error of 3. My thinking is that it shouldnt do that because the else statment doesnt happen because add0 = "na". What i need it to do: When i enter na it should write to file as na and when i enter 8 numbers it should run the iName variable. This is my code that i have tried i just need to know what i have done wrong.

 
String add0 = newn.getText();
String non = "na";
 
            if(add0=="na"){
                out.write(non.getBytes());
            }else{
                 String iName = ("Updated Number: " + add0.substring(0, 3) + "-" + add0.substring(3, 5) + "-" + add0.substring(5) + newLine);
                    out.write(iName.getBytes());
            }