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Sorting Collections

aslika bahini
Ranch Hand

Joined: Mar 03, 2007
Posts: 111

pg 549-550 k&B Book

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
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
You might


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

marc weber

Joined: Aug 31, 2004
Posts: 11343

Originally posted by samura babu: 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?

"We're kind of on the level of crossword puzzle writers... And no one ever goes to them and gives them an award." ~Joe Strummer
Jesper de Jong
Java Cowboy
Saloon Keeper

Joined: Aug 16, 2005
Posts: 14913

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 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 ]

    Java Beginners FAQ - JavaRanch SCJP FAQ - The Java Tutorial - Java SE 8 API documentation
    aslika bahini
    Ranch Hand

    Joined: Mar 03, 2007
    Posts: 111
    successfully done populateList()

    Thanks Jesper Young
    subject: Sorting Collections
    It's not a secret anymore!