Page 569-571 : Formatting output AND making program in book (Generics and collections)

[Rahul Sudip Bose]

I will read details of a movie from a text file, dump them into an array list, sort the array list . Print list before and after it was sorted.

The text file has lines in this format :
movie name/genre/actor/year

How do i save each of the details of a movie in separate strings (say, of a movie object)...ie store the words after every / in a new variable.
I made a basic program which is ok, but i want my output not to have any slash / . How can i achieve this ?

Here is the output :

before sort
[wedding crashers/romantic-comedy/owen wilson/2008, the ring/horror/freaky girl ?/2004, the terminator 3/sci-fi,action/arnold schwarznegger/2009, the hangover/c
omedy/???/2010, 2012/sci-fi/???/2010]
after sort
[2012/sci-fi/???/2010, the hangover/comedy/???/2010, the ring/horror/freaky girl ?/2004, the terminator 3/sci-fi,action/arnold schwarznegger/2009, wedding crash
ers/romantic-comedy/owen wilson/2008]

Here is the program :

import java.io.*;
import java.util.*;
public class DVDinfo
{
static File movies = new File("movies");
static File myDVD = new File(movies,"myDVD.txt") ;
static ArrayList<String> al;
public static void main(String[] args)
{
try
{
movies.mkdir();
myDVD.createNewFile();
al = new ArrayList<String>();
FileReader fr = new FileReader(myDVD);
BufferedReader br = new BufferedReader(fr);
String temp = null;
while((temp = br.readLine()) != null)
{
al.add(temp);
}//while ends
br.close();
System.out.println("\n\nbefore sort \n\n"+al);
Collections.sort(al);
System.out.println("\n\nafter sort \n\n"+al);
}catch(Exception e){e.printStackTrace();}
}//main ends
}//class ends

[Mohamed Sanaulla]

You can create a Movie class- with the fields as there in the text file- Name, genre, actor, year. Then when you read a line from the file- you can use the split() function of the String to split the sentence based on the separator. And each string thus obtained can be used to create a new Movie instance and then add the instance to the ArrayList. You need to implement Comparable interface in the Movie class so that Collection.sort() can sort the contents of the list correctly. Also you can override toString method in Movie class so that it displays a neatly formatted String when ever the name of the Movie instance is used.

[Rahul Sudip Bose]

 

Mohamed Sanaulla wrote:Then when you read a line from the file- you can use the split() function of the String to split the sentence based on the separator. And each string thus obtained can be used to create a new Movie instance and then add the instance to the ArrayList.

That part was successfully implemented here :

public class splitter
{
public static void main(String[]args)
{
String path = "c\\games\\demos\\mygame";
System.out.println("path is " + path);
String[] demo = path.split("\\\\");
for(String x : demo)System.out.println(x);
}
}
/*OUTPUT :
path is c\games\demos\mygame
c
games
demos
mygame
*/

(the progress for above code in this post : https://coderanch.com/t/533203/java/java/String-split-Runtime-Error-program#2418134 )

[Rahul Sudip Bose]

the text file to be processed contains this :
________________________________________
wedding crashers/romantic-comedy/2008
the ring/horror/2004
the terminator 3/sci-fi,action/2009
the hangover/comedy/2010
2012/sci-fi/2010
________________________________________

Now the full code which uses the above code to process this text file :
This code throws runtime exception which is shown after the program.

import java.util.*;
import java.io.*;
class DVD
{
private String title;
private String genre;
private String year;
public DVD(String title, String genre , String year)
{
this.title = title;
this.genre = genre;
this.year = year;
}
public void showDVD()
{
System.out.println("DVD :- " +"\tTITLE : "+ title +"\tGENRE: "+genre+"\tYEAR: "+year);
}
public String[] getDVD()
{
String [] DVD = {title,genre,year};
return DVD;
}
}//class ends
class DVDLib
{
public static void main(String[] args)
{
List<DVD> myVids = new ArrayList<DVD>();
File movies = new File("movies");
File myDVD = new File(movies,"myDVD.txt");
try
{
movies.mkdir();
myDVD.createNewFile();
System.out.println("file and directory success !"); // TEST CODE !
}catch(Exception ex){ex.printStackTrace();}
myVids = populateDVDList(myDVD);
System.out.println("\n\nthe discs in your collection are :\n\n" + myVids);
}//main ends
public static ArrayList<DVD> populateDVDList(File file)
{
ArrayList<DVD> discs = null;
try
{
FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);
String temp = null;
String [] DVDdetails = null;
while( (temp=br.readLine())!= null)
{
System.out.println("temp is " + temp); // TEST CODE !
DVDdetails = temp.split("////"); // NOTICE THIS LINE !
for(String x : DVDdetails)System.out.println("current dvd detail is " + x); // TEST CODE !
String t = DVDdetails[0]; // get title of dvd
String g = DVDdetails[1]; // get genre of dvd
String y = DVDdetails[2]; // get years of dvd
discs.add(new DVD(t,g,y));
}//while ends
}catch(Exception ex){ex.printStackTrace();}
return discs;
}// method ends
}// class ends

Runtime exception :

file and directory success !
temp is wedding crashers/romantic-comedy/2008
java.lang.ArrayIndexOutOfBoundsException: 1
at DVDLib.populateDVDList(DVDLib.java:68)
at DVDLib.main(DVDLib.java:45)
the discs in your collection are :
null

[Mohamed Sanaulla]

Look at the separator used for the split function. (The thread you had posted which had the run time error use- "\" as the separator and this one is using "/")- Did you try using just "/"?

Suggestion: >> Before operating on the Array using indexes- Ensure that the array is of the required size

[Rahul Sudip Bose]

 

Mohamed Sanaulla wrote:Look at the separator used for the split function. (The thread you had posted which had the run time error use- "\" as the separator and this one is using "/")- Did you try using just "/"?

Suggestion: >> Before operating on the Array using indexes- Ensure that the array is of the required size

New program works !!!

Did all that you told me, thanks for giving those crucial clues. One small problem remains in the output, tab between title and year is there only for first movie and not for the others ???

now only one feature to be added, ie sorting as per given parameter like title, year etc. will add it soon.

regards
rb

PS : the code and output below...

[Rahul Sudip Bose]

THE CODE :

import java.util.*;
import java.io.*;
class DVD
{
private String title;
private String genre;
private String year;
public DVD(String title, String genre , String year)
{
this.title = title;
this.genre = genre;
this.year = year;
}
public String toString()
{
String dvdDetails = "\n\n\nDVD TITLE>> " + title + "\n\n@GENRE>> "+ genre +"\t@YEAR>> " + year +"\n";
return dvdDetails;
}
public String[] getDVD()
{
String [] DVD = {title,genre,year};
return DVD;
}
}//class ends
class DVDLib
{
public static void main(String[] args)
{
List<DVD> myVids = new ArrayList<DVD>();
File movies = new File("movies");
File myDVD = new File(movies,"myDVD.txt");
try
{
movies.mkdir();
myDVD.createNewFile();
}catch(Exception ex){ex.printStackTrace();}
myVids = populateDVDList(myDVD);
System.out.println("\n\nthe discs in your collection are :\n\n" + myVids);
}//main ends
public static List<DVD> populateDVDList(File file)
{
List<DVD> discs = new ArrayList<DVD>();
try
{
FileReader fr = new FileReader(file);
BufferedReader br = new BufferedReader(fr);
String temp = null;
String [] DVDdetails = null;
while( (temp=br.readLine())!= null)
{
DVDdetails = temp.split("/");
String t = DVDdetails[0]; // get title of dvd
String g = DVDdetails[1]; // get genre of dvd
String y = DVDdetails[2]; // get years of dvd
discs.add(new DVD(t,g,y));
}//while ends
}catch(Exception ex){ex.printStackTrace();}
return discs;
}// method ends
}// class ends

THE OUTPUT :

/*OUTPUT :
the discs in your collection are :
[
DVD TITLE>> wedding crashers
@GENRE>> romantic-comedy @YEAR>> 2008
,
DVD TITLE>> the ring
@GENRE>> horror @YEAR>> 2004
,
DVD TITLE>> the terminator 3
@GENRE>> sci-fi,action @YEAR>> 2009
,
DVD TITLE>> the hangover
@GENRE>> comedy @YEAR>> 2010
,
DVD TITLE>> 2012
@GENRE>> sci-fi @YEAR>> 2010
]
*/