can't concat strings

BulldogLowell:
char array may be better, but if you want to understand String class look at it this way

adding a string constant to a string constant is not allowed...

myString = "this string" + "that string";  //nope

you have to add your string constant to a string:

void setup()

{
  String myString;
  myString = myString + "foo";
  myString += "bar";
  Serial.print(myString);
}

Ok so the concatenation is happening before the assignment and not during it.