16 - Comparable and Comparator - level basic - Java 1.6.0_17 - NB 6.8

public class DVD implements Comparable {

    String title;
    String genre;
    String leadActor;

    DVD(String t, String g, String a) {
        title = t;
        genre = g;
        leadActor = a;
    }

    String getGenre() {
        return genre;
    }

    @Override
    public String toString() {
        return title + " " + genre + " " + leadActor;
    }

    public int compareTo(DVD o) {
        //throw new UnsupportedOperationException("Not supported yet.");
        return title.compareTo(o.title);
    }
}

import java.util.Comparator;

public class GenreSort implements Comparator {

    public int compare(DVD o1, DVD o2) {

        //throw new UnsupportedOperationException("Not supported yet.");

        return o1.getGenre().compareTo(o2.getGenre());

    }

}

import java.util.ArrayList;

import java.util.Collections;

public class TestDVD {

    ArrayList dvdList = new ArrayList();

    void populateList() {

        dvdList.add(new DVD("title5", "genre4", "actor2"));

        dvdList.add(new DVD("title4", "genre3", "actor1"));

        dvdList.add(new DVD("title3", "genre2", "actor4"));

        dvdList.add(new DVD("title2", "genre1", "actor6"));

        dvdList.add(new DVD("title1", "genre2", "actor6"));

    }

    void go() {

        populateList();

        System.out.println("dvdlist :" + dvdList);

        Collections.sort(dvdList);

        System.out.println("dvdlist :" + dvdList);

        GenreSort gs  = new GenreSort();

        Collections.sort(dvdList, gs);

        System.out.println("dvdlist :" + dvdList);

    }

    public static void main(String[] args) {

        new TestDVD().go();

    }

}

run:

dvdlist :[title5 genre4 actor2, title4 genre3 actor1, title3 genre2 actor4, title2 genre1 actor6, title1 genre2 actor6]

dvdlist :[title1 genre2 actor6, title2 genre1 actor6, title3 genre2 actor4, title4 genre3 actor1, title5 genre4 actor2]

dvdlist :[title2 genre1 actor6, title1 genre2 actor6, title3 genre2 actor4, title4 genre3 actor1, title5 genre4 actor2]

A) The class implements Comparable (is thus modified) and the list is sorted on titles.

B) A new Comparator is implemented and the class is sorted on genres using the class GenreSort.

C) You can avoid to return something from a method if you throw an Exception. Did you know that ?