28. String concatenation example

• Code that adds dashes to a phone number:

  
  String phoneNumber1 = "9775551212";
  String phoneNumber2 = phoneNumber1.substring(0, 3);
  phoneNumber2 += "-";
  phoneNumber2 += phoneNumber1.substring(3, 6);
  phoneNumber2 += "-";
  phoneNumber2 += phoneNumber1.substring(6);