public String toString$()$

Returns a String representing the characters stored in grid in a format that is

easy to read, that exactly matches the format given below.

o $($new LetterCrush$(4,3,$"AACADBBDCD"$)).$toString$()$ must return

Note the row number at the end of the $2^{nd}$ to $4^{th}$ lines, and the column numbers in

the last row. The column indices will always be one$-$digit values $($grids with widths

greater than nine will not be tested$).$

public boolean isStable$()$

Returns false if there is any position in grid where a non$-$EMPTY character is

above an EMPTY character $($a grid entry with a smaller row than a grid entry with

a larger row in the same column $-$ thus, for the example given above in the

description of the toString$()$ method, isStable$()$ would return false$).$

Otherwise, returns true.