Complete the implementation of a generic matrix class. a matrix is a two-dimensional arrangement of elements. you access elements with a row and column index. for example,
matrixtttboard = new matrix(3,3);
tttboard. put(0,0,"x");
if (tttboard. get(1,2).equals("o"
if the matrix has many rows and columns but few elements, it doesn't make sense to allocate a large two-dimentinal array, most of whose entries are null. instead, we will only store the non-null entries in a map. we store the (i, j) element at the key with value i * columns + j. for example, in a 10 x 10 matrix, the (3,4) element has key 3 * 10 + 4 = 34.

complete the implementations of the get and put method below.
complete the following code:
import. java. util. map;
import. java. util. treemap;
public class matrix
{
public matrix(int rows, int columns)
{
this. rows = rows;
this. columns = columns;
elements = new treemap();
} //add your get and put methods here
private mapelements;
private int rows;
private int columns;
// the following method is used to check your work
public static string check(int r, int c, string s)
{
int rows = 3;
int columns = 4;
matrixm = new matrix(rows, columns);
// add letters of s diagonally
for (int i = 0; i < s. length(); i++)
{m. put(r, c,s. substring(i, i+1));
r++; if (r > = rows) r = 0;
c++; if (c > = columns) c = 0;
} //make string representing matrix content

string t = "";

for (int i = 0; i < rows; i++)

for (int j = 0; j < columns; j++)

if (m. get(i, j) == null)

t += ".";

else

t += m. get(i, j);

return t;

}

}