Null pointer displaying cannot find error

Question

NULL POINTER Error message is displayed when running my programme. code is attached but cannot seem to find the problem.

Exception in thread "main" java.lang.NullPointerException at coursework2.Assignment.main(Assignment.java:330

  lastName = last;
  firstName = first;
  email = pemail;
  dob = pdob;
  town = ptown;
  job = pjob;
  school = pschool;
  status = pstatus;
  //String[] friendArray;
  friendArray = new String[]{lastName,firstName,email,dob,town,job,school,status};



  String searchName;
  int input;
  int index;

  SimpleDateFormat dateFormat= new SimpleDateFormat ("dd/mm/yyy");
  SimpleDateFormat timeFormat= new SimpleDateFormat ("hh:mm");
  SimpleDateFormat birthdayFormat= new SimpleDateFormat ("dd/mm");

  Date today = new Date();

  dateFormat.format(today);           //get current date time with date()
  timeFormat.format(today);           //get current date time with calender ()
  birthdayFormat.format(today);       //get current
  Calendar.getInstance();

  //int length = friendList.length;
  int maxSize = 100;                                                    // array size
  User arr;                                                         // reference to array
  arr = new User(maxSize);                                         // create the array
  User [] userList = new User[500];

  friendArray = new String[]{lastName};
  userList[0].setFriendArray("Henly");
  userList[0].setFriendArray("White");

  userList[1].setFriendArray("Davidson");
  userList[1].setFriendArray("White");

  userList[2].setFriendArray("Browne");
  userList[2].setFriendArray("Gomez");

  userList[3].setFriendArray("Browne");
  userList[3].setFriendArray("Reid");

  userList[4].setFriendArray("White");
  userList[4].setFriendArray("Henly");

  userList[5].setFriendArray("Myles");
  userList[5].setFriendArray("Browne");

  userList[6].setFriendArray("Davidson");
  userList[6].setFriendArray("Browne");

  userList[7].setFriendArray("White");
  userList[7].setFriendArray("Gomez");

  userList[8].setFriendArray("Reid");
  userList[8].setFriendArray("Scott");

It wont allow me to post all my code! However Line 30 is friendArray = new String[]{lastName}; userList[0].setFriendArray("Henly"); userList[0].setFriendArray("White"); — user3592094, Jun 19 '14 at 11:02
You didn't initialize userList[0], so it is null. You have to do something like: `userList[0] = new User();`. And you have to do this for each element in the `userList` array. — eternay, Jun 19 '14 at 11:09
My userList array consists of several : arr.insert("White", "Emma", "white92@hotmail.com", "25/05/1992", "Belfast", "Student", "Victoria College", "Finally the weekend!!", friendArray); // insert items — user3592094, Jun 19 '14 at 11:18
possible duplicate of [What is a Null Pointer Exception, and how do I fix it?](http://stackoverflow.com/questions/218384/what-is-a-null-pointer-exception-and-how-do-i-fix-it) — Josef E., Jun 19 '14 at 17:39

score 0 · Answer 1 · answered Jun 19 '14 at 17:12

This code creates an array with null in every slot:

User [] userList = new User[500];

a couple of lines down, you try to use userList[0]:

userList[0].setFriendArray("Henly");

...but userList[0] is still null. You have to create a User object and assign it to that entry, e.g.:

userList[0] = new User(/*...any necessary arguments here...*/);

Then you can do this:

userList[0].setFriendArray("Henly");

...because userList[0] is no longer null.

Obviously, this is true for indexes 1, 2, 3, and so on.

Side note: Elsewhere, you have:

User arr;

I would strongly advise that you don't call something arr that isn't an array.

Null pointer displaying cannot find error

1 Answers1