BoggleSolution.java

static void solver(BoggleBoard board) {
        for (int i = 0; i < board.getRows(); i++) {
            for (int j = 0; j < board.getColumns(); j++) {
                solver(board, board.getCharAt(i,j) + "", i, j);
            }
        }
    }

    static private void solver(
            BoggleBoard board,
            String word,
            int x, int y)
    {

        if (trie.containsWord(word) && !answer.contains(word)) {
            answer.add(word);
            counter++;
        }

        if (!trie.containsPrefix(word)) { return; }

        //upper left
        if (0 <= x - 1 && 0 <= y - 1 && !board.isVisited(x - 1,y - 1)){
            solver(board, word+board.getCharAt(x-1,y-1), x-1, y-1);
        }

        //up
        if (0 <= y - 1 && !board.isVisited(x,y - 1)){
            solver(board, word + board.getCharAt(x,y-1), x, y-1);
        }

        //upper right
        if (x + 1 < board.getRows() && 0 <= y - 1 && !board.isVisited(x + 1,y - 1)){
            solver(board, word+board.getCharAt(x+1,y-1), x+1, y-1);
        }

        //right
        if (x + 1 < board.getRows() && !board.isVisited(x + 1,y)){
            solver(board, word + board.getCharAt(x+1,y), x+1, y);
        }

        //lower right
        if (x+1 < board.getRows() && y+1 < board.getColumns() && !board.isVisited(x+1,y+1)){
            solver(board, word+board.getCharAt(x+1,y+1), x+1, y+1);
        }

        //down
        if (y + 1 < board.getColumns() && !board.isVisited(x,y + 1)){
            solver(board, word + board.getCharAt(x,y+1), x, y+1);
        }

        //lower left
        if (0 <= x - 1 && y + 1 < board.getColumns() && !board.isVisited(x - 1,y + 1)){
            solver(board, word+board.getCharAt(x-1,y+1), x-1, y+1);
        }

        //left
        if (0 <= x - 1 && !board.isVisited(x - 1,y)){
            solver(board, word + board.getCharAt(x-1,y), x-1, y);
        }
    }