Grid.java

package model;

import java.util.Iterator;
import java.util.List;
import java.util.Random;


/**
 * {@link Grid} instances represent the grid in <i>The Game of Life</i>.
 */
public class Grid implements Iterable<Cell> {

    private final int numberOfRows;
    private final int numberOfColumns;
    private final Cell[][] cells;

    /**
     * Creates a new {@code Grid} instance given the number of rows and columns.
     *
     * @param numberOfRows    the number of rows
     * @param numberOfColumns the number of columns
     * @throws IllegalArgumentException if {@code numberOfRows} or {@code numberOfColumns} are
     *                                  less than or equal to 0
     */
    public Grid(int numberOfRows, int numberOfColumns) {
        this.numberOfRows = numberOfRows;
        this.numberOfColumns = numberOfColumns;
        this.cells = createCells();
    }

    /**
     * Returns an iterator over the cells in this {@code Grid}.
     *
     * @return an iterator over the cells in this {@code Grid}
     */

    @Override
    public Iterator<Cell> iterator() {
        return new GridIterator(this);
    }

    private Cell[][] createCells() {
        Cell[][] cells = new Cell[getNumberOfRows()][getNumberOfColumns()];
        for (int rowIndex = 0; rowIndex < getNumberOfRows(); rowIndex++) {
            for (int columnIndex = 0; columnIndex < getNumberOfColumns(); columnIndex++) {
                cells[rowIndex][columnIndex] = new Cell();
            }
        }
        return cells;
    }

    /**
     * Returns the {@link Cell} at the given index.
     *
     * <p>Note that the index is wrapped around so that a {@link Cell} is always returned.
     *
     * @param rowIndex    the row index of the {@link Cell}
     * @param columnIndex the column index of the {@link Cell}
     * @return the {@link Cell} at the given row and column index
     */
    public Cell getCell(int rowIndex, int columnIndex) {
        return cells[getWrappedRowIndex(rowIndex)][getWrappedColumnIndex(columnIndex)];
    }

    private int getWrappedRowIndex(int rowIndex) {
        return (rowIndex + getNumberOfRows()) % getNumberOfRows();
    }

    private int getWrappedColumnIndex(int columnIndex) {
        return (columnIndex + getNumberOfColumns()) % getNumberOfColumns();