Comparing two Vectors

Question

I have a vector which initially reads a file line by line and is displayed by an applet. The file has 'N' constant lines & is dynamic . When the applet gets refreshed, the file is read into an another Vector. Now how do i compare the two vectors i.e in case there is any change in the new Vector the new 'n' lines should be appended to the old vector by replacing the 'n' lines.
Thanks

Answer 1

If I understand your question correctly, you have an input file of fixed length (for argument's sake, we will say 5 lines) as in:
line #1
line #2
line #3
line #4
line #5You read these lines into a Vector (we'll call it Vector A). Some time passes, and you look at the file again, and it's contents are:
line #3
line #4
line #5
line #6
line #7Now you read these lines into Vector B. This is the part I get confused about. If you are just planning on detecting change(i.e., remove 1 & 2, add 6 & 7), why not just overwrite Vector A with Vector B?
If you need to know specifically which lines are new, you could write simple methods:
* This method will return a Vector containing the lines no longer in
* the file.
* @param vecOld the Old Vector
* @param vecNew the New Vector
* @return a Vector containing entries in Old not found in New
public Vector findRemovals(Vector vecOld, Vector vecNew) {
  Vector vecReturn = new Vector();
  for (int i = 0; i < vecOld.size(); i++) {
    if (!vecNew.contains(vecOld.get(i))) {
      vecReturn.add(vecOld.get(i));
  return vecReturn;
* This method will return a Vector containing the new lines in
* the file.
* @param vecOld the Old Vector
* @param vecNew the New Vector
* @return a Vector containing entries in New not found in Old
public Vector findAdditions(Vector vecOld, Vector vecNew) {
  Vector vecReturn = new Vector();
  for (int i = 0; i < vecNew.size(); i++) {
    if (!vecOld.contains(vecNew.get(i))) {
      vecReturn.add(vecNew.get(i));
  return vecReturn;
}I hope this helps. If not, could you post a clearer description of your problem?