Collections.sort() on Array List

[Sandra Bachan]

Hello,

Below is code I created based on Sierra/Bates Chapter 7. It compiles and runs; I have a related question. See below.

import java.util.*;
import java.io.*;

class DVDInfo implements Comparable<DVDInfo>{
	String title;
	String genre;
	String leadActor;
	
	DVDInfo(String t, String g, String a){
		title = t; genre = g; leadActor = a;
	}
	
	public String toString(){
		return title + " " + genre + " " + leadActor + "\n";
	}
	
	public int compareTo(DVDInfo d){
		return title.compareTo(d.getTitle());
	}
	
	public String getTitle(){
		return title;
	}
	
	public String getGenre(){
		return genre;
	}
		
	public String getLeadActor(){
		return leadActor;
	}
	
	public void setTitle(String t){
		title = t;
	}
	
	public void setGenre(String g){
		genre = g;
	}
	public void setLeadActor(String l){
		leadActor = l;
	}
	
	
}

public class MyDVD{
	public static void main(String[] args){
		ArrayList<DVDInfo> dvdList = new ArrayList<DVDInfo>();
		populateList(dvdList);
		
		Collections.sort(dvdList);
		System.out.println(dvdList);
		
	}
	
	public static void populateList(ArrayList<DVDInfo> dvdList){
		try{	
			File file = new File("dvdinfo.txt"); 
			FileReader fr = new FileReader(file);
			BufferedReader br = new BufferedReader(fr);
		
			String s;
			while ((s = br.readLine()) != null){
				String[]tokens = s.split("/");
				dvdList.add(new DVDInfo(tokens[0],tokens[1],tokens[2]));
			}
			br.close();
		}catch(IOException e){System.out.println("File doesn\'t exist");}
		
	}
	
}

This following is output:

[2001 sci-fi ??
, Caddy Shack comedy Murray, Bill
, Donnie Darko sci-fi Gyllenhall, Jake
, Lost in Translation comedy Murray, Bill
, Patriot Games action Ford, Harrison
, Raiders of the Lost Ark action Ford, Harrison
, Star Wars sci-fi Ford, Harrison
]


Is there another way this code can compare dvdList without having DVDInfo extend Comparable? Sierra/Bates mentions:

Returning to our earlier example for class DVDInfo, we can take the easy way out and use the String class’s implementation of compareTo():

class DVDInfo implements Comparable<DVDInfo> {	// #1 // existing code 
   public int compareTo(DVDInfo d) {
      return title.compareTo(d.getTitle());	// #2
   }
}

Please clarify what is the un-easy way to compare dvdList?

[Tom Reilly]

Take a look at java.util.Comparator

[Alpesh Padra]

You can implement sorting by 2 way

1. Comparable
2. Comparator with compare(T o1, T o2) method

[Abimaran Kugathasan]

Is this you want? Check and reply....

import java.util.*;
import java.io.*;

class DVDInfo {
	String title;
	String genre;
	String leadActor;

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

	public String toString(){
		return title + " " + genre + " " + leadActor + "\n";
	}

	public String getTitle(){
		return title;
	}

	public String getGenre(){
		return genre;
	}

	public String getLeadActor(){
		return leadActor;
	}

	public void setTitle(String t){
		title = t;
	}

	public void setGenre(String g){
		genre = g;
	}
	public void setLeadActor(String l){
		leadActor = l;
	}


}

public class SortWithComparetor	{
	public static void main(String[] args){
		ArrayList<DVDInfo> dvdList = new ArrayList<DVDInfo>();
		populateList(dvdList);

		System.out.println("Without ordering\n");
		//Collections.sort(dvdList);
		System.out.println(dvdList);

		System.out.println("\nWith Genere order\n");

		SortByGenere sg = new SortByGenere();
		Collections.sort(dvdList, sg);
		System.out.println(dvdList);

	}

	public static void populateList(ArrayList<DVDInfo> dvdList){
			try{
				File file = new File("dvdinfo.txt");
				FileReader fr = new FileReader(file);
				BufferedReader br = new BufferedReader(fr);

				String s;
				while ((s = br.readLine()) != null){
					String[]tokens = s.split("\\.");
					int len = tokens.length;
					Outer:
					for(int i = 0;i < len;i+=3)	{
							dvdList.add(new DVDInfo(tokens[i],tokens[i+1],tokens[i+2]));
							if(((i + 1) / 3) == 0)	{
								continue;
							}
					}
				}
				br.close();
			}catch(IOException e){System.out.println("File doesn\'t exist");}

	}

}

class SortByTitle implements Comparator<DVDInfo>	{
	public int compare(DVDInfo one, DVDInfo two)	{
		return one.getTitle().compareTo(two.getTitle());
	}
}

class SortByGenere implements Comparator<DVDInfo>	{
	public int compare(DVDInfo one, DVDInfo two)	{
		return one.getGenre().compareTo(two.getGenre());
	}
}

[Kunal Lakhani]

Abimaran Kugathasan
Please don't provide any code.