JAVA: Preventing Duplicate Entries to an ArrayList

Question

I am trying to prevent duplicate entries from being added to an ArrayList as the list is being populated whilst reading through each line of a file. Each line of the file is

Answer 1

If you want to keep the order of the lines read keep using the list but for the duplicates you can use a set for determining if a line (in its two forms as you described) was already added :

Set duplicates = new HashSet();
while((line = bufferedReader.readLine()) != null) {

     String delimiter = "\t";
     String[] tempnodelist;  
     tempnodelist = line.split(delimiter);

     String lineReversed = tempnodelist[1] + delimiter + tempnodelist[0];

     if (!duplicates.contains(line) && !duplicates.contains(lineReversed )) {
         edges.add(line);
     }
}