record Cell(int row, int col) {}

void main() {
    // Storing values on a grid, keyed by cell
    Map<Cell, String> board = new LinkedHashMap<>();
    board.put(new Cell(0, 0), "X");
    board.put(new Cell(1, 1), "O");
    board.put(new Cell(2, 2), "X");

    IO.println(board.get(new Cell(1, 1)));
    IO.println(board.containsKey(new Cell(0, 0)));
    IO.println(board.containsKey(new Cell(0, 1)));
}

// From Groundwork, chapter 10 (ch10-records), box 4.
// This example is from Groundwork, licensed CC BY-NC-SA 4.0.
// Run with: java ch10_04.java