Reading a file

Files are means of persistance. Peristance refers to the ability to keep, store & contain data, without a running program.

When a program stops executing, all of the variables, data and state are effectively wiped from memory.

File formats

Files have different formats - some are human readable such as .txt files others are meant to be read by a machine such as a .class file.

We will be working with .csv files.

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A .csv file is structured as a table, meaning that it has columns & rows, each row representing an entity.

Each of the rows in the .csv file above represents a movie (entity) from IMDB.

How to read files

The approach to reading files in java is to refer to the file on disk by its path.

The file is afterwards read by a scanner in a loop and each loop iteration refers to a line in the file.

Files can both be read word by word - or in our context line by line.

In the example we will be consuming a file line by line and printing it to the screen.

Pseudo-code

Refer to the file on disk

Read it with a scanner

While the scanners has input

​ Print the file

Setup

New directory created for resources such as data files

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File placed in the folder (dragged and dropped)

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Code

package algorithms.data.structures;

import java.io.File;
import java.io.FileNotFoundException;
import java.util.Scanner;

public class FileReader {
    public static void main(String[] args){
        try{
            File filmFile = new File("resources/film-imdb.csv");
            Scanner sc = new Scanner(filmFile);
            while(sc.hasNextLine()){
                String movieDetails = sc.nextLine();
                System.out.println(movieDetails);
            }
        }catch(FileNotFoundException e){
            System.out.println("Could not find file");
        }
    }
}

Exercise: Movie-Analysis

End product:

A console based program that reads a data-set and provides the user with detailed insight about movies

Data

movies.csv

Components

FileReader: A class that reads a file with a method that returns an arraylist of movie objects

(1) Implement functionality such that you can print each movie string from the film-imdb.csv file

(2) Refactor the code such that each movie are stored as Movie objects in an arraylist

AnalysisEngine

An object that instantiates & calls the FileReader method.

AnalysisEngine implements methods to find answers for the following questions:

• What movie has the longest name?

• How many movies are from the Star Trek franchise?

• What is the average length for a movie in hours?

• What is the highest amount of words in a movie title from the list?

  • Example:

  • Wagon master has 2 words

  • Tie Me Up! Tie Me Down! has 6 words

  • Tie Me Up! Tie Me Down! has the maximum amount of words of this 2 title example

• How many movies won awards?

Advanced analysis

• What year won the most awards?

• How many movies are sequals?

• What movie has the most unique consonant?

(Optional) Menu

• Write a menu that lets the user choose what question he/she wants answered