Sorting Collections

[aslika bahini]

pg 549-550 k&B Book

    
    class DVDInfo {
String title;
String genre;
String leadActor;
DVDInfo(String t, String g, String a) {
Sorting Collections and Arrays (Exam Objective 6.5) 549
title = t; genre = g; leadActor = a;
}
public String toString() {
return title + " " + genre + " " + leadActor + "\n";
}
// getters and setter go here
}

Here's the DVD data that's in the dvdinfo.txt file:
Donnie Darko/sci-fi/Gyllenhall, Jake
Raiders of the Lost Ark/action/Ford, Harrison
2001/sci-fi/??
Caddy Shack/comedy/Murray, Bill
Star Wars/sci-fi/Ford, Harrison
Lost in Translation/comedy/Murray, Bill
Patriot Games/action/Ford, Harrison

I didn't understand the following paragraph

we want to create an instance of DVDInfo
for each line of data we read in from the dvdinfo.txt file. For each instance, we will parse the line of data (remember String.split()?) and populate DVDInfo's three instance variables. Finally, we want to put all of the DVDInfo instances into an ArrayList. Imagine that the populateList() method (below) does all of this. Here is a small piece of code from our application:

ArrayList<DVDInfo> dvdList = new ArrayList<DVDInfo>();
populateList(); // adds the file data to the ArrayList
System.out.println(dvdList);
You might

question:

how does populateList of method looks with necessary coding?
can any one help with coding to understand populateList() method

Thanks
samura

[marc weber]

Originally posted by samura babu:
...how does populateList of method looks with necessary coding?
can any one help with coding to understand populateList() method...

Coding this method is excellent practice for the exam, because it uses a number of different features. Give it a try, and let us know where you're stuck.

The first step is to just read in each line of the text file. Can you write code for this?

[Jesper de Jong]

What exactly did you not understand? I'll try to write it in different words, I hope that will help:

There is a file named "dvdinfo.txt".

You have to write a method 'populateList()' that opens the file and reads it line by line.

For each line in the file, you create a new DVDInfo object.

You initialize each DVDInfo object with the information that you find on each corresponding line.

You add each DVDInfo object to an ArrayList of DVDInfo objects.

At the end of the method, you return that ArrayList.

Some hints:

You can use java.io.BufferedReader to read a file line by line (example: Java - Reading text files).

As the text suggests, you split the line into separate items (title, genre, actor) by using String.split().

Have a look at the Java API documentation of BufferedReader, String.split() and ArrayList.

Try writing the code yourself. If you get stuck, then please post what you have written so far and explain where you get stuck.
[ June 29, 2007: Message edited by: Jesper Young ]

[aslika bahini]

successfully done populateList()

    
 
import java.io.*;
import java.util.*;
 
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:  "+ title + "    GENRE:" + genre + "  Actor :" + leadActor + "\n";
 }
 public int compareTo(DVDInfo d)
 {
 return title.compareTo(d.getTitle());
 }
 public String getTitle()
 {
 return title;
 }
 
 }
 

public class populatList {

ArrayList <DVDInfo> dvdInfoList = new ArrayList<DVDInfo>();

public void printAllDVDInfo()
{
System.out.println("***********************************");
for(int i=0; i< dvdInfoList.size();i++)
System.out.println(dvdInfoList.get(i));
Collections.sort(dvdInfoList);
System.out.println("***********************************");

}

public static ArrayList<String> splitSentence(String sentence) {

ArrayList<String> al = new ArrayList<String>();
 
     String[] result = sentence.split("/");
    
         for (int x=0; x<result.length; x++)
         {
        
        al.add(result[x]);
         }              
   

      return al;
  }

 public void populateList()
    {
      
        
      
        try
        {
            File file = new File("dvdinfo.txt");
            FileReader fr = new FileReader(file);
            BufferedReader bfr = new BufferedReader(fr);
            
            String sentence = bfr.readLine();
            
            while (sentence != null)
            {
            
            ArrayList<String> splitList = splitSentence(sentence);
            DVDInfo info = new DVDInfo(splitList.get(0), splitList.get(1), splitList.get(2));
            dvdInfoList.add(info);
            
            sentence = bfr.readLine();
            }
                                 
            
            fr.close();
           
        }catch(IOException e)        
        {
            e.printStackTrace();
        }
        
}
        public static void main(String[] args)
        {
        populatList plist = new populatList();
        plist.populateList();
        plist.printAllDVDInfo();
        }
    
}

Thanks Jesper Young