Introduction to Classes - Learning Java Through Games - page 128

public static final boolean VERTICAL = false ;
public static final int [ ] placement = { 5,4,3,2,2,1,1 } ;
The first constant stores the size of the board, where the program only works with a
square board. The next two constants define the horizontal and vertical direction, while
the last constant lists the sizes of the ships that will be placed on the board. This design
is elegant because it allows us to easily change the board size or the ship sizes without
modifying any other code.
For every board, we will store the ships and cells that make up the board. Here is the
definition of the two variables:
Ship [] ships = new Ship [ placement . length ] ;
Cell[][] grid = new Cell [BOARDSIZE ] [ BOARD SIZE ] ;

Note that the number of ships is equal to the size of the placement array.
Next, we present the constructor of the Board class. As expected, it will simply initialize
the instance variables of the class (i.e., the variables ships and grid ).
public class Board {
...
public Board() {
populateGrid() ;
populateShips () ;

}

public void populateGrid() {

for ( int row = 0; row < BOARD SIZE ; row++) {

for ( int col = 0; col < BOARD SIZE ; c o l ++) {

grid [row][ col ] = new Cell () ;

}

}

}

public void populateShips () {
for ( int i=0; i < placement . length ;

i++) {

ships [ i]= new Ship(placement [ i ] , this );

}

}

}

The constructor is split into two methods. The populateGrid method creates the cells,
while the populateShips method creates the ships and adds them to the array of ships. The
for loop in the populateShips method traverses the placement array. For each element of
the array, the method creates a ship with the required size and adds the ship to the ships
array. Note that, as expected, the new keyword is called multiple times on the ships array.
It is called once to create the array and then again for each element of the array. When we
call the constructor of the Ship class, the second parameter is the this reference because
the Ship class needs access to the board object.
Next, we show the toString method of the Board class. It traverses the cells of the grid
and calls the toString method on each cell of the grid.
public String toString() {
String result = " 0123456789\n ----------" ;
int line = 0;

for (Cell[] row: grid) {
result+= "\n" ;