I have been told what to write, but im very confused on how exactly im supposed
ID: 3607044 • Letter: I
Question
I have been told what to write, but im very confused on how exactly im supposed to write out this code, any help would be appreciated.
Lab7:
// Your job is to complete this program so that it runs correctly.
// The Movie class and MovieDB class have already been completed for you.
// Utilizing data abstraction, you can access/use these classes without
// having to know their implementation details. However, since you have
// the code for them you certainly can look at the implementations.
// You just need to write the correct code in the 3 passages below. Some
// comments indicate what you need to do in each case.
import java.util.*;
import java.io.*;
public class Lab7
{
public static void main(String [] args) throws IOException
{
MovieDB movies = new MovieDB(10); // Create MovieDB object. The
// size is set at 10, meaning it can hold up to 10
// movies. If we wanted (as discussed in lecture) we
// could allow for it to be resized so it could hold
// an arbitrary number of movies.
loadData(movies); // input movie data from file
getCommands(movies); // interact with user
saveData(movies); // save movie data back to file
}
public static void loadData(MovieDB movies) throws IOException
{
// Note the syntax below for creating a Scanner to a file
Scanner S = new Scanner(new FileInputStream("movieFile.txt"));
// *** CODE SEGMENT 1 *** //
// Complete this method in the following way:
// Read in the number of movies from the file
// For each movie read the data from the file and create a Movie
// object
// Add the Movie to the MoviesDB object (movies) using the appropriate
// method (see MovieDB class)
}
public static void getCommands(MovieDB movies)
{
Scanner inScan = new Scanner(System.in);
System.out.println("Enter your choice:");
System.out.println("1. List movies");
System.out.println("2. Add new movie");
System.out.println("3. Find movie");
System.out.println("4. Quit");
String choice = inScan.nextLine();
while (true)
{
Movie temp;
if (choice.equals("1"))
{
System.out.println(movies.toString());
}
else if (choice.equals("2"))
{
// *** CODE SEGMENT 2 *** //
// Complete this choice in the following way:
// Prompt for and read in each of the values needed
// for the new Movie object (3 strings, 1 double)
// Create a new Movie object and then add it to the
// MovieDB object (movies) using the correct method.
}
else if (choice.equals("3"))
{
// *** CODE SEGMENT 3 *** //
// Complete this choice in the following way:
// Ask the user for the movie name and read it in
// Call the appropriate method in the MovieDB object
// (movies) to find the Movie and return it
// Show the movie's info (or indicate it is not found)
}
else
{
System.out.println("Good-bye");
break; // any other value -- quit
}
System.out.println("Enter your choice:");
System.out.println("1. List movies");
System.out.println("2. Add new movie");
System.out.println("3. Find movie");
System.out.println("4. Quit");
choice = inScan.nextLine();
}
}
public static void saveData(MovieDB movies) throws IOException
{
PrintWriter P = new PrintWriter("movieFile.txt");
// Note that we are printing the entire DB to the file with
// one statement. This is because the toStringFile() method
// of the MovieDB class calls the toStringFile() method of
// each Movie within the DB.
P.print(movies.toStringFile());
P.close();
}
}
Movie:
import java.text.*;
import java.util.*;
public class Movie
{
private String title;
private String director;
private String studio;
private double gross;
// Constructor -- take 4 arguments and make a new Movie
public Movie(String t, String d, String s, double g)
{
title = new String(t);
director = new String(d);
studio = new String(s);
gross = g;
}
// Return a formatted string version of this Movie
public String toString()
{
StringBuffer B = new StringBuffer();
B.append("Title: " + title + " ");
B.append("Director: " + director + " ");
B.append("Studio: " + studio + " ");
NumberFormat formatter = NumberFormat.getCurrencyInstance(Locale.US);
B.append("Gross: " + formatter.format(gross) + " ");
return B.toString();
}
// Return an unformatted string version of this Movie
public String toStringFile()
{
StringBuffer B = new StringBuffer();
B.append(title + " ");
B.append(director + " ");
B.append(studio + " ");
B.append(gross + " ");
return B.toString();
}
// Accessor to return title of this Movie
public String getTitle()
{
return title;
}
}
MovieDB:
// This class is a simple database of Movie objects. Note the
// instance variables and methods and read the comments carefully.
public class MovieDB
{
// Note that we have 2 instance variables here -- an array of Movie and
// an int. Since Java arrays are of fixed size once they are created,
// we creating the array of a certain (large) size and then using the
// int variable to keep track of how many actual movies are in it. We
// don't resize here, but we could if we wanted to (as discussed in class).
private Movie [] theMovies;
private int numMovies;
// Initialize this MovieDB
public MovieDB(int size)
{
theMovies = new Movie[size];
numMovies = 0;
}
// Take already created movie and add it to the DB. This is simply putting
// the new movie at the end of the array, and incrementing the int to
// indicate that a new movie has been added. If no room is left in the
// array, indicate that fact.
public void addMovie(Movie m)
{
if (numMovies < theMovies.length)
{
theMovies[numMovies] = m;
numMovies++;
}
else
System.out.println("No room to add movie");
// Alternatively, as we discussed in lecture, we could resize the
// array to make room - feel free to try this as an additional
// exercise.
}
// Iterate through the array until the movie is found or the end of the
// array is reached. Note that even though a Movie object has several
// components we are searching based on the title alone. We call the
// title the "key value" for the Movie. If the Movie is not found we
// indicate that fact by returning null.
public Movie findMovie(String title)
{
for (int i = 0; i < numMovies; i++)
{
if (theMovies[i].getTitle().equals(title))
return theMovies[i];
}
return null;
}
// Return a formatted string containing all of the movies' info. Note
// that we are calling the toString() method for each movie in the DB.
public String toString()
{
StringBuffer B = new StringBuffer();
B.append("Movie List: ");
for (int i = 0; i < numMovies; i++)
B.append(theMovies[i].toString() + " ");
return B.toString();
}
// Similar to the method above, but now we are not formatting the
// string, so we can write the data to the file.
public String toStringFile()
{
StringBuffer B = new StringBuffer();
B.append(numMovies + " ");
for (int i = 0; i < numMovies; i++)
B.append(theMovies[i].toStringFile());
return B.toString();
}
}
MovieFile.txt:
3
Star Wars
George Lucas
20th Century Fox
7.98E8
Jaws
Steven Spielberg
Universal
4.706E8
The Return of the King
Peter Jackson
New Line
1.1292E9
Sample Output:
Explanation / Answer
The program with code filled in the three code segments is as follows ( comments have been added to explain the code) :
import java.util.*;
import java.io.*;
public class Lab7
{
public static void main(String [] args) throws IOException
{
MovieDB movies = new MovieDB(10); // Create MovieDB object. The
// size is set at 10, meaning it can hold up to 10
// movies. If we wanted (as discussed in lecture) we
// could allow for it to be resized so it could hold
// an arbitrary number of movies.
loadData(movies); // input movie data from file
getCommands(movies); // interact with user
saveData(movies); // save movie data back to file
}
public static void loadData(MovieDB movies) throws IOException
{
// Note the syntax below for creating a Scanner to a file
Scanner S = new Scanner(new FileInputStream("movieFile.txt"));
// *** CODE SEGMENT 1 *** //
// Complete this method in the following way:
// Read in the number of movies from the file
// For each movie read the data from the file and create a Movie
// object
// Add the Movie to the MovieDB object (movies) using the appropriate
// method (see MovieDB class)
int numMovies=Integer.parseInt(S.nextLine());
for(int i=0; i<numMovies; i++){
String movieName=S.nextLine();
String director=S.nextLine();
String studio=S.nextLine();
Double gross=Double.parseDouble(S.nextLine());
Movie movie=new Movie(movieName, director, studio, gross);
//created the movie object, now add it to MovieDB object (movies)
movies.add(movie);
}
}
public static void getCommands(MovieDB movies)
{
Scanner inScan = new Scanner(System.in);
System.out.println("Enter your choice:");
System.out.println("1. List movies");
System.out.println("2. Add new movie");
System.out.println("3. Find movie");
System.out.println("4. Quit");
String choice = inScan.nextLine();
while (true)
{
Movie temp;
if (choice.equals("1"))
{
System.out.println(movies.toString());
}
else if (choice.equals("2"))
{
// *** CODE SEGMENT 2 *** //
// Complete this choice in the following way:
// Prompt for and read in each of the values needed
// for the new Movie object (3 strings, 1 double)
// Create a new Movie object and then add it to the
// MovieDB object (movies) using the correct method.
System.out.println(“Enter movie name”); //prompting the user to enter value
String movieName=inScan.nextLine();
System.out.println(“Enter director name”);
String director=inScan.nextLine();
System.out.println(“Enter studio name”);
String studio=inScan.nextLine();
System.out.println(“Enter gross amount for movie”);
Double gross=Double.parseDouble(inScan.nextLine());
Movie newMovie=new Movie(movieName, director, studio, gross);
//created the movie object, now add it to MovieDB object (movies)
movies.add(newMovie);
}
else if (choice.equals("3"))
{
// *** CODE SEGMENT 3 *** //
// Complete this choice in the following way:
// Ask the user for the movie name and read it in
// Call the appropriate method in the MovieDB object
// (movies) to find the Movie and return it
// Show the movie's info (or indicate it is not found)
System.out.println(“Enter movie name”);
String title=inScan.nextLine();
Movie movieFound=movies.findMovie(title);
if(movieFound==null) //movie not found
System.out.println(“Movie with this title not found”);
else{
System.out.println(“Movie information: “+movieFound.toString());
} // print formatted information of movie
}
else
{
System.out.println("Good-bye");
break; // any other value -- quit
}
System.out.println("Enter your choice:");
System.out.println("1. List movies");
System.out.println("2. Add new movie");
System.out.println("3. Find movie");
System.out.println("4. Quit");
choice = inScan.nextLine();
}
}
public static void saveData(MovieDB movies) throws IOException
{
PrintWriter P = new PrintWriter("movieFile.txt");
// Note that we are printing the entire DB to the file with
// one statement. This is because the toStringFile() method
// of the MovieDB class calls the toStringFile() method of
// each Movie within the DB.
P.print(movies.toStringFile());
P.close();
}
}
Movie:
import java.text.*;
import java.util.*;
public class Movie
{
private String title;
private String director;
private String studio;
private double gross;
// Constructor -- take 4 arguments and make a new Movie
public Movie(String t, String d, String s, double g)
{
title = new String(t);
director = new String(d);
studio = new String(s);
gross = g;
}
// Return a formatted string version of this Movie
public String toString()
{
StringBuffer B = new StringBuffer();
B.append("Title: " + title + " ");
B.append("Director: " + director + " ");
B.append("Studio: " + studio + " ");
NumberFormat formatter = NumberFormat.getCurrencyInstance(Locale.US);
B.append("Gross: " + formatter.format(gross) + " ");
return B.toString();
}
// Return an unformatted string version of this Movie
public String toStringFile()
{
StringBuffer B = new StringBuffer();
B.append(title + " ");
B.append(director + " ");
B.append(studio + " ");
B.append(gross + " ");
return B.toString();
}
// Accessor to return title of this Movie
public String getTitle()
{
return title;
}
}
MovieDB:
// This class is a simple database of Movie objects. Note the
// instance variables and methods and read the comments carefully.
public class MovieDB
{
// Note that we have 2 instance variables here -- an array of Movie and
// an int. Since Java arrays are of fixed size once they are created,
// we creating the array of a certain (large) size and then using the
// int variable to keep track of how many actual movies are in it. We
// don't resize here, but we could if we wanted to (as discussed in class).
private Movie [] theMovies;
private int numMovies;
// Initialize this MovieDB
public MovieDB(int size)
{
theMovies = new Movie[size];
numMovies = 0;
}
// Take already created movie and add it to the DB. This is simply putting
// the new movie at the end of the array, and incrementing the int to
// indicate that a new movie has been added. If no room is left in the
// array, indicate that fact.
public void addMovie(Movie m)
{
if (numMovies < theMovies.length)
{
theMovies[numMovies] = m;
numMovies++;
}
else
System.out.println("No room to add movie");
// Alternatively, as we discussed in lecture, we could resize the
// array to make room - feel free to try this as an additional
// exercise.
}
// Iterate through the array until the movie is found or the end of the
// array is reached. Note that even though a Movie object has several
// components we are searching based on the title alone. We call the
// title the "key value" for the Movie. If the Movie is not found we
// indicate that fact by returning null.
public Movie findMovie(String title)
{
for (int i = 0; i < numMovies; i++)
{
if (theMovies[i].getTitle().equals(title))
return theMovies[i];
}
return null;
}
// Return a formatted string containing all of the movies' info. Note
// that we are calling the toString() method for each movie in the DB.
public String toString()
{
StringBuffer B = new StringBuffer();
B.append("Movie List: ");
for (int i = 0; i < numMovies; i++)
B.append(theMovies[i].toString() + " ");
return B.toString();
}
// Similar to the method above, but now we are not formatting the
// string, so we can write the data to the file.
public String toStringFile()
{
StringBuffer B = new StringBuffer();
B.append(numMovies + " ");
for (int i = 0; i < numMovies; i++)
B.append(theMovies[i].toStringFile());
return B.toString();
}
}
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