Question

JAVA! Algorithm using Java Collections Framework. Please only answer if you can help...

Basically we need to find an algorithm using an EFFICIENT JCF in order to get to the solution... for this problem, I need to go through a text file and output only the last 8888 lines in order that they appear...if there are fewer lines, then print all of those... But my code is too slow because I store the all lines (s.add(lines)) i think...and I can't find a way to make it faster ! How can I make this work correctly and fast?

public static void doIt(BufferedReader r, PrintWriter w) throws IOException {
   ArrayList s = new ArrayList<>();
   ArrayList t = new ArrayList<>();


   for (String line = r.readLine(); line != null; line = r.readLine()) {
      s.add(line);
   }

   if (s.size() <= 8888) {
      for (int i = 0; i < s.size(); i++) {
         t.add(s.get(i));
      }
   } else if (s.size() > 8888) {
      for (int i = s.size() - 8888; i < s.size(); i++) {
         t.add(s.get(i));
      }
   }
   System.out.println(t);
}

Answer 1

public static void doIt(BufferedReader r, PrintWriter w) throws IOException {
       ArrayList s = new ArrayList<String>();
       ArrayList t = new ArrayList<String>();
       Queue q = new PriorityQueue<String>();

       for (String line = r.readLine(); line != null; line = r.readLine()) {
           s.add(line);
           if (q.size() < 8888)
               q.add(line);
           else {
               q.remove();
               q.add(line);
           }
       }
       t.addAll(q);

      
   }

// if the the count increases than q will remove the first inserted lines and keeps the latest lines so it only keeps the 8888

so finally we are adding the all values from q to t