Java implementation

Exercise 3.13. In many applications, matrices are sparse. They have mostly values of zero off the diagonal, values of one on the diagonal, and a few other values: [1 0 a 0] 0 1 0 0 O Ob 1 Lo o o 1 Such a matrix can be stored more efficiently by simply keeping track of the special values and their row and column positions. Reimplement the Matrix class of Exercise 3.12 using a representation that is optimized for sparse matrices