Homework 4: Java

First read initial 4 Chapters of Core Java I. Download Java to some machine you can use. Test on "Hello World". Then solve this problem

Writing a Java application with class structure

The aim of this assignment is to give you some practice with Java syntax and make sure that you understand the class concept.

Design and implement a class, Matrix to represent matrices. You will probably need three instance variables in the class:

   int nrows ;    // The number of rows
   int ncols ;    // The number of columns
   float [][];    // Array holding the elements of the matrix

Write a constructor that takes two arguments--the number of rows and columns--and allocates an array to hold the elements.

You should also write the following public methods.

• A set method with three arguments i, j, x, which assigns floating point value x to the (i, j) element of the matrix.
• A get method with two arguments i, j, which returns the value of the (i, j) element of the matrix.
• inquiry methods getNumRows and getNumCols which respectively return the numbers of rows and columns.
• An add method which adds together two matrices and returns a new matrix containing the sum of the two matrices, element by element
• A multiply method which multiplies together the two matrices according to the proper rules of matrix multiplication, and returns a new matrix containing the product of the two matrices.

The methods add and multiply may be implemented either as instance methods or as static methods on the Matrix class: you should decide which you think is most suitable and explain your reasons.

You should also write a test program for this class. For now (because we haven't covered keyboard input yet) create a few small matrices and initialize their element values values within the program. Calculate suitable sum(s) and product(s) using your add and multiply methods. Print the elements of the original matrices, and of the sums and products, using the System.out.println method illustrated in the lectures (to get a nice lay-out, it may also help to use System.out.print, which is similar but doesn't automatically end with a new-line).