• WriterComparator.java

  • § 
    package MusicLandscape.util.comparators;

import MusicLandscape.entities.Track;

import java.util.Comparator;
  • §

    Comparators are quite simple, they only need to implement the compare(T t1, T t2) method that compares two objects of the type T.

    /**
 * Encapsulates the concept of comparing two tracks by writer.
 *
 * @author Jonas Altrock (ew20b126@technikum-wien.at)
 * @version 1
 * @since ExerciseSheet05
 */
public class WriterComparator implements Comparator<Track> {
    /**
     * Compares two tracks by writer.<br>
     * The natural ordering of artists is used.
     *
     * @param o1 the first object to be compared.
     * @param o2 the second object to be compared.
     * @return a negative integer, zero, or a positive integer as the
     * first argument is less than, equal to, or greater than the
     * second.
     * @throws NullPointerException if an argument is null and this
     *                              comparator does not permit null arguments
     * @throws ClassCastException   if the arguments' types prevent them from
     *                              being compared by this comparator.
     */
    @Override
    public int compare(Track o1, Track o2) {
  • §

    We delegate to Artist.compareTo, which we can do because we implement the Comparable interface there.

            return o1.getWriter().compareTo(o2.getWriter());
    }

    /**
     * the string representation is "by writer" (without quotes)
     *
     * @return a string representation of the object.
     */
    @Override
    public String toString() {
        return "by writer";
    }
}