Implement a class Grid that stores measurements in a rectangular grid. The grid has

a given number of rows and columns, and a description string can be added for any

grid location. Supply the following constructor and methods:

public Grid(int numRows, int numColumns)

public void add(int row, int column, String description)

public String getDescription(int row, int column)

public ArrayList getDescribedLocations()

Here, Location is an inner class that encapsulates the row and the column of a grid

location.