CS 1054: Project 4: Using Arrays (Summer 2005)

Assigned Date: 6/14/2005
Due Date: 6/18/2005 (at midnight)
Points: 80

You will start using arrays in this project.

Problem description (Programming problem 5.23 from textbook)

Write a program with a method to multiply two matrices. The header of the method is as follows

public static int[][] multiplyMatrix(int[][] a, int[][] b)

To multiply matrix a by matrix b, the number of columns in a must be the same as the number of rows in b, and the two matrices must have elements of the same or compatible types. Let c be the result of the multiplication, and a, b, and c are denoted as follows:

where

Sample input and output

Your program should read in the matrix values from two separate input files. The first input file is called matrix1.txt and the second input file is called matrix2.txt Each file looks like this:

The first line indicates the dimensions of the matrix. If matrix1.txt was the above file and matrix2.txt looked like this:

the result of the matrix multiplication should be stored in a file called matrixproduct.txt. For the above two input files, the output would look exactly the same as matrix1.txt, since the 2nd matrix is the identity matrix and would be

You should print out the dimensions of the product matrix as the first line of the output file.

Hints and suggestions

You should check to see if the dimensions of the two input matrices are valid for multiplication.
You need to use two nested for-loops to read in the values for the input matrices and store them into a file.
You need to use three nested for-loops to calculate the matrix product.
Store all values as int.
Since your input for this program comes from files, you should use the File class in conjunction with the Scanner class. For example, you could use the following code to open a Scanner for reading in the first matrix:
```
String matrixFilename1 = "matrix1.txt";
Scanner matrixScanner1 = new Scanner(new File(matrixFilename1));
```

Your output also goes to a file. You can use the following code to write to the correct output file:

String matrixProductFilename = "matrixProduct.txt";
PrintWriter matrixProduct = new PrintWriter(new File(matrixProductFilename));

Refer to your lab exercises, programs 1 and 2, and class notes if you need more help. Also remember that the instructor and GTA are there to help you. Do not hesitate to contact them for any sort of help that you need.

Additional samples of input and correct output are available on the course website.

Evaluation

Your program will be submitted to the Curator system. You will have five submissions. You will not be given more submissions for any reason! Your submitted program will be graded by the GTA. There will be no automatic grading for any project in this course. You will receive your grade via email from the class account cs1054@cs.vt.edu in the form of a grade-sheet. This project will be evaluated for style and design as well as correctness. Make sure you follow the standard Java conventions for indentation, variable names and documentation in your program. Look at programs 1 and 2 for examples of acceptable documentation. 60 of the 80 points will be correctness, while 20 points will be for style and documentation.

Submitting your Program

As indicated earlier, you will submit this assignment to the Curator System (read the Student Guide). Instructions for submitting are contained in the Student Guide. You will be allowed up to five submissions for this assignment. Use them wisely. Test your program thoroughly before submitting it. It is advisable to show your program to the instructor or the TA to make sure it works correctly before submitting it. Make sure that your program produces correct results for every sample input file posted on the course website. The Student Guide can be found at: http://www.cs.vt.edu/curator/

Program Compilation

Your program must compile and run under JDK 1.5.

Pledge

Every program submission for this class must include an Honor Code pledge. Specifically, you must always include the following pledge statement in the header comment for your program:

/****************************************************************************
 *
 * On my honor:
 *
 * - I have not discussed the Java language code in my program with
 * anyone other than my instructor or the teaching assistants
 * assigned to this course.
 *
 * - I have not used Java language code obtained from another student,
 * or any other unauthorized source, either modified or unmodified.
 *
 * - If any Java language code or documentation used in my program
 * was obtained from another source, such as a text book or course
 * notes, that has been clearly noted with a proper citation in
 * the comments of my program.
 *
 * - I have not designed this program in such a way as to defeat or
 * interfere with the normal operation of the Curator System.
 *
 * Your Name
 * Your PID
****************************************************************************/

Failure to include this pledge in a submission is a violation of the Honor Code.