Putting an object instance into an ArrayList

[Shamsudeen Akanbi]

Hi guys, in this home automation application, I want to create an instance of DVDInfo for each line of data I read in from the dvdInfo.txt file. For each instance, I will parse the line of data and populate DVDInfo's three instance variables. Finally, I want to put all of the DVDInfo instances into an ArrayList.

[Jeff Verdegan]

Do you have a question?

What have you tried so far and what part(s) gave you trouble? And exactly what kind of trouble?

[Shamsudeen Akanbi]

hey sorry I thought I added it! Here it is:


import java.util.*;
import java.io.*;
class DVDInfo {
private String title;
private String genre;
private 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 static void populateList() {
try {
File dvdDir = new File("dvdDir");
dvdDir.mkdir();
File dvdFile = new File("dvdDir", "dvdInfo.txt");
dvdFile.createNewFile();
FileWriter fw = new FileWriter(dvdFile);
BufferedWriter bw = new BufferedWriter(fw);
bw.write("Donnie Darko/sci-fi/Gyllenhall, Jake");
bw.newLine();
bw.write("Raiders of the Lost Ark/action/Ford, Harrison");
bw.newLine();
bw.write("2001/sci-fi/??");
bw.newLine();
bw.write("Caddy Shack/comedy/Murray, Bill");
bw.newLine();
bw.write("Star Wars/sci-fi/Ford, Harrison");
bw.newLine();
bw.write("Lost in Translation/comedy/Murray, Bill");
bw.newLine();
bw.write("Patriot Games/action/Ford, Harrison");
bw.flush();
bw.close();

FileReader fr = new FileReader(dvdFile);
BufferedReader br = new BufferedReader(fr);
String data;
while( (data = br.readLine()) != null) { //prints each line of
//text from the file

String[] token = data.split("/"); //splits the string
DVDInfo dvd = new DVDInfo(token[0], token[1], token[2]);

System.out.println(dvd);
}
fr.close();
} catch(IOException e) { e.printStackTrace(); }
}
public static void main(String[] args) {
ArrayList<DVDInfo> dvdList = new ArrayList<DVDInfo>();
populateList();
System.out.println(dvdList);

}
}

Hey bro, its well edited now. I don't understand how to put each instances of the DVDInfo I read and splited into the ArrayList.

[Jeff Verdegan]

1) Please go back and edit your post to UseCodeTags.(⇐click) You'll probably need to re-paste it, since the indenting will already have been lost.

2) You still haven't answered these two important questions that I asked in my first reply: What part(s) gave you trouble? And exactly what kind of trouble?

[Shamsudeen Akanbi]

okay got it

[Shamsudeen Akanbi]

import java.util.*;   
import java.io.*;   
class DVDInfo {   
    private String title;   
    private String genre;   
    private 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 static void populateList() {   
        try {   
          File dvdDir = new File("dvdDir");    
         dvdDir.mkdir();   
         File dvdFile = new File("dvdDir", "dvdInfo.txt");   
         dvdFile.createNewFile();   
         FileWriter fw = new FileWriter(dvdFile);   
         BufferedWriter bw = new BufferedWriter(fw);   
         bw.write("Donnie Darko/sci-fi/Gyllenhall, Jake");   
         bw.newLine();   
         bw.write("Raiders of the Lost Ark/action/Ford, Harrison");   
         bw.newLine();   
         bw.write("2001/sci-fi/??");   
         bw.newLine();   
         bw.write("Caddy Shack/comedy/Murray, Bill");   
         bw.newLine();   
         bw.write("Star Wars/sci-fi/Ford, Harrison");   
         bw.newLine();   
         bw.write("Lost in Translation/comedy/Murray, Bill");   
         bw.newLine();   
         bw.write("Patriot Games/action/Ford, Harrison");   
         bw.flush();   
         bw.close();   
        
         FileReader fr = new FileReader(dvdFile);   
         BufferedReader br = new BufferedReader(fr);   
         String data;   
         while( (data = br.readLine()) != null) {   //prints each line of   
                                                                   //text from the file   
  
             String[] token = data.split("/"); //splits the string   
             DVDInfo dvd = new DVDInfo(token[0], token[1], token[2]);   //my problem lies here I guess!
  
             System.out.println(dvd);   
         }   
         fr.close();   
         } catch(IOException e) { e.printStackTrace(); }   
    }   
    public static void main(String[] args) {   
        ArrayList<DVDInfo> dvdList = new ArrayList<DVDInfo>();   
        populateList();    
        System.out.println(dvdList);   
  
    }   
}   

Hey bro, its well edited now. I don't understand how to put each instances of the DVDInfo I read and splited into the ArrayList.

[Mohamed Sanaulla]

Hi Shamsudeen, I have edited the post and reformatted the code for you, so that its more clearer for the person reading it.

Coming back to your query: you are creating a new ArrayList instance but your populateList method is not aware of this instance because the scope of the reference variable you are using is limited to the main() method. You can pass around the reference to the populateList method and let the method take care of adding the DVDInfo to the list. So it would be something like:

void populateList(List<DVDInfo> dvdList)
{
  //... reading and writing
  DVDInfo dvd = new DVDInfo(all the params)
  dvdList.add(dvd);
}

main()
{
  List<DVDInfo> dvdList = new ArrayList<DVDInfo>();
  populateList(dvdList)
}

PS: the code I have given above is syntactically not correct, its just an idea of how you can fix your code.