Working solution to the 2016 AP Computer Science Crossword free response question :: https://compsci.rocks/crossword-solution/

constructor.java

public Crossword(boolean[][] blackSquares) {
		puzzle = new Square[blackSquares.length][blackSquares[0].length];
		int num = 1;
		
		for (int r=0; r<blackSquares.length; r++) {
			for (int c=0; c<blackSquares[r].length; c++) {
				if (blackSquares[r][c]) {
					puzzle[r][c] = new Square(true, 0);
				}
				else {
					if (toBeLabeled(r, c, blackSquares) {
						puzzle[r][c] = new Square(false, num);
						num++;
					}
				else {
					puzzle[r][c] = new Square(false, 0); 
				}
			}
		}
	}

Crossword.java

public class Crossword {
	
	private Square[][] puzzle; 
	
	private boolean toBeLabeled( int r, int c, boolean[][] blackSquares ) {
		return (!(blackSquares[r][c]) &&
			( r == 0 || c == 0 || blackSquares[r-1][c] || blackSquares[r][c-1] );
	}
	
	public Crossword(boolean[][] blackSquares) {
		puzzle = new Square[blackSquares.length][blackSquares[0].length];
		int num = 1;
		
		for (int r=0; r<blackSquares.length; r++) {
			for (int c=0; c<blackSquares[r].length; c++) {
				if (blackSquares[r][c]) {
					puzzle[r][c] = new Square(true, 0);
				}
				else {
					if (toBeLabeled(r, c, blackSquares) {
						puzzle[r][c] = new Square(false, num);
						num++;
					}
				else {
					puzzle[r][c] = new Square(false, 0); 
				}
			}
		}
	}
}

Square.java

public class Square {
  public Square( boolean isBlack, int num ) {
    /* Implementation not shown */ 
  }
  
  // There may be instance variables, constructors, and
  // methods that are not shown
}

toBeLabeled.java

private boolean toBeLabeled( int r, int c, boolean[][] blackSquares ) {
  return (!(blackSquares[r][c]) && ( r == 0 || c == 0 || blackSquares[r-1][c] || blackSquares[r][c-1] );
}