Type safety: Unchecked cast from Object to ArrayList

Question

Here is a part of a program that sends an ArrayList from a server to a client. I want to remove the warning about the last line in this code:

Client code:

Answer 1

Try this

Object obj = ois.readObject();
// Check it's an ArrayList
if (obj instanceof ArrayList) {
  // Get the List.
  ArrayList al = (ArrayList) obj;
  if (al.size() > 0) {
    // Iterate.
    for (int i = 0; i < al.size(); i++) {
      // Still not enough for a type.
      Object o = al.get(i);
      if (o instanceof MyVariable) {
        // Here we go!
        MyVariable v = (MyVariable) o;
        // use v.
      }
    }
  }
}