CS 160, Spring 2015
Programming Assignment P11
Music Library: Classes, Objects, and Arrays

Programming due Monday, Apr. 27 at 6:00pm; late deadline Apr. 27 at 11:59pm.

1. Declare a class with data and methods
2. Write your first constructor
3. Allocate and instantiate an array of objects
4. Continue practicing file input and output

Description

1. Create a new project in Eclipse called P11.
2. Define a new class called Music.java, with a main method.
3. Define the following as private instance (non-static) data in Music.java:

       private String songTitle;
       private String albumName;
       private String artistName;
       private int releaseYear;
       

4. Define a constructor that is passed data used to initialize all the instance variables. A constructor is just like a normal method except it has no return value. Next write methods to get individual variables, as shown below. The methods should be public and non-static, and should have the exact signatures shown below:

       // Constructor
       public Music(String title, String album, String artist, int year) { }
   
       // Get methods
       public String getTitle() { }
       public String getAlbum() { }
       public String getArtist() { }
       public int getYear() { }
       

5. Write a toString method that returns a string with the title, album, artist, and year, separated by commas and a space, with no trailing comma or space. The string should match the the sample output shown in Part Three. This method should NOT print anything, instead it creates a string and returns it!

   	// toString method
   	public String toString() {}
       

6. Implement the following method to get the price of the title:

       public double getPrice() { }
       

   The algorithm for determining the price is $1.29 for titles released before 1970, $1.89 for titles released in the 1970's, $0.69 for titles released in the 1980's, $0.99 for titles released in the 1990's, and $1.39 for titles released on 2000 and later. The reasoning for this is that some decades have better music than others!

1. In the class you have already made called Music.java:
2. Declare (but do not allocate) an array of Music objects called arrayTitles as a public static class variable.
3. Implement a public static method readLibrary which takes a String parameter with the input filename:

       public static void readLibrary(String inputFile);
       

4. Call readLibrary from your main with args[0] as the parameter.
5. Do not hard-code the file name, use the name passed in as a parameter.
6. Here is the data file that you will read for this program: music.txt
7. Implement readLibrary as follows:
   
   
   • Add a scanner to read from the file whose name is passed in.
   • You will need a try-catch block for this to work.
   • If the file cannot be read, print an error message and exit the program.
   • Read the number of titles, an integer, from the file.
   • Use the number of titles to allocate the array of Music objects.
   • Add a for or while loop that reads the remaining lines of the file.
   • The format is 4 lines per entry: title, album, artist, year.
   • Store each title from the file in a corresponding Music object in the array.
8. NOTE: Even after allocating the array, you must instantiate each individual Music object (by calling the constructor) for each array element.
9. WARNING: After each call to nextInt() you must add a nextLine() call to discard the newline that follows the integer, otherwise the next string you read may be empty. Add print statements if necessary to make sure you are reading all the data correctly.

1. Implement a public static method writeLibrary which takes a String parameter with the output filename:

       public static void writeLibrary(String outputFile);
       

2. Call writeLibrary from your main (after readLibrary) with args[1] as the parameter.
3. Do not hard-code the file name, use the name passed in as a parameter.
4. To implement writeLibrary, open a PrintWriter and write a loop to iterate the array of Music objects, writing out each entry as shown by the example output file below:

   1: Brown Eyed Girl, Blowin' Your Mind!, Van Morrison, 1967
   2: Stop Putting the Hurt on Me, Lucille, B. B. King, 1968
   3: Another Brick in the Wall, The Wall, Pink Floyd, 1979
   4: Funeral for a Friend, Goodbye Yellow Brick Road, Elton John, 1973
   5: Beat It, Thriller, Michael Jackson, 1982
   6: Like a Virgin, Like a Virgin, Madonna, 1984
   7: So Far Away, Brothers in Arms, Dire Straits, 1985
   8: Try a Little Tenderness, Swamp Boogie Queen, Katie Webster, 1990
   9: Hey Jack Kerouac, MTV Unplugged, 10,000 Maniacs, 1993
   10: Mockingbird, Encore, Eminem, 2005
   11: Jackdaw, Draw the Line, David Gray, 2009
   12: Someone Like You, 21, Adele, 2011
   Total cost: $14.58
       

5. Your output file should match this exactly.
6. The format above has a number for each title, starting at 1 and ending at the last number. Each field is separated by a comma and space, but there is no trailing comma or space.
7. Make sure that your program correctly writes all of the data in the input file to the output file.
8. Add code to writeLibrary figure out how much it would cost to buy all the titles in the file by iterating the array of Music objects and calling getPrice for each element. You must accumulate the total cost in a variable. Write the message below to the output file using PrintWriter.printf() to ensure 2 digits after the decimal point in the total cost.

Testing

• Work on your own.
• The name of the source code file must be exactly Music.java
• Comments at the top with your name, e-Name, date and course.
• We expect programming assignments to be implemented in Eclipse using Java 1.5 or 1.6 or 1.7 or 1.8.
• We will be testing the code on the machines in the CS computer lab, so make sure your code runs on those machines.
• We will be checking programs for plagiarism, so please don't copy from anyone else.

Grading Criteria

• 100 points for perfect submission.
• 0 points for no submission, will not compile, submitted class file, etc.
• Preliminary Tests
  • compileTest: checks that program compiles. (0 points)
  • test1: checks that methods in the Music class are declared as specified. (10 points)
  • test2: checks that data in the Music class are declared as specified. (10 points)
  • test3: tests the constructor and getters for the Music class. (10 points)
  • test4: tests the getPrice method in the Music class. (10 points)
  • test5: checks the size of the allocation of arrayTitles in the Music class. (10 points)
  • test6: checks that the data in arrayTitles is correctly filled in. (10 points)
  • Preliminary grading uses the supplied data file (music.txt).
• Final Tests
  • Using a file of unspecified name and contents that we provide, test the following:
  • test7: checks the output file contents, using music.txt. (10 points)
  • test8: checks the format and accuracy of the total cost, using music.txt. (10 points)
  • test9: checks the output file contents, using another file. (10 points)
  • test10: checks the format and accuracy of the total cost, using another file. (10 points)
  • Final grading includes the preliminary tests, and uses an unspecified data file.

Submission