How to calculate the median for every insertion in a priority queue in java?

Question

I read objects(Movies) from a file and i compare based on their likes. I want to get the median after every Movie insertion in the queue. In the code below there are :

• Movie method compareTo
• PQ insert and getMax methods with swim and sink
• Main class

I'm creating both priority queues for higher and less objects than median, but i don't know how to dynamically calculate it. Every movie element is created with id, title, likes in this order.

public int compareTo(Movie m) {
        if (this.likes == m.likes) {
            return -this.title.compareTo(m.title);
        } else if (this.likes > m.likes) {
            return 1;
        } else {
            return -1;
        }

    }

---

public class PQ {

    private Movie[] pq;
    private int size;

    public PQ(int capacity) {
        if (capacity < 1) {
            throw new IllegalArgumentException();
        }
        this.pq = new Movie[capacity + 1];
        this.size = 0;
    }

    public void insert(Movie movie) {

        if (this.size == this.pq.length - 1) {
            throw new IllegalArgumentException();
        }
        if (movie == null) {
            throw new IllegalArgumentException();
        }

        this.size++;
        this.pq[this.size] = movie;
        swim(this.size);
    }

    public void swim(int i) {

        while (i > 1) {
            int p = i / 2;
            int result = this.pq[p].compareTo(this.pq[i]);
            if (result <= 0)
                return;
            swap(i, p);
            i = p;
        }
    }

    public Movie Max() {
        if (this.size == 0)
            throw new IllegalArgumentException();
        return this.pq[1];
    }

    public Movie getMax() {
        if (this.size == 0)
            throw new IllegalArgumentException();
        Movie m = this.pq[1];
        if (this.size > 1)
            this.pq[1] = this.pq[this.size];
        this.pq[this.size--] = null;
        sink(1);
        return m;
    }

    private void sink(int i) {
        int left = 2 * i;
        int right = left + 1;
        int max = left;
        while (left <= this.size) {
            if (right <= this.size) {
                max = this.pq[right].compareTo(this.pq[left]) < 0 ? right
                        : left;
            }
            if (this.pq[max].compareTo(this.pq[i]) >= 0)
                return;
            swap(i, max);
            i = max;
            left = 2 * i;
            right = left + 1;
            max = left;
        }
    }

    private void swap(int i, int j) {
        Movie tmp = pq[i];
        pq[i] = pq[j];
        pq[j] = tmp;
    }

}

---

import java.io.BufferedReader;
import java.io.FileReader;
import java.io.IOException;

public class Dynamic_Median {
    public static void main(String[] args) {

        BufferedReader br = null;
        PQ higher_median = new PQ(4);
        PQ less_median = new PQ(4);
        Movie median = null;
        try { // try to read the file

            br = new BufferedReader(new FileReader("movies.txt"));
            String line;
            String title = "";
            int id = 0;
            int likes = 0;

            while ((line = br.readLine()) != null) {
                line = line.trim();
                line = line.replaceAll("/t", "");
                String[] tokens = line.split(" "); // store every token in an
                                                    // String array
                id = Integer.parseInt(tokens[0]);
                likes = Integer.parseInt(tokens[tokens.length - 1]);
                for (int i = 1; i < tokens.length - 1; i++) {
                    title = title + " " + tokens[i];
                }
                title = "";
            }

        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Answer 1

ki esy re kopela mou teleftaia mera ths prothesmias thymithikes na rwthseis? :P