I'm having a hell of a time trying to figure out how to make captured stones disappear. I've read everywhere that I should use the flood fill algorithm, but I haven't had any luck with that so far. Any help would be amazing! Here is my code:

package Go;

import static java.lang.Math.*;
import static stdlib.StdDraw.*;
import java.awt.Color;

public class Go2 {

    public static Color opposite(Color player) {
        if (player == WHITE) {
            return BLACK;
        }
        return WHITE;
    }

    public static void drawGame(Color[][] board) {
        Color[][][] unit = new Color[400][19][19];
        for (int h = 0; h < 400; h++) {
            for (int x = 0; x < 19; x++) {
                for (int y = 0; y < 19; y++) {
                    unit[h][x][y] = YELLOW;
                }
            }
        }
        setXscale(0, 19);
        setYscale(0, 19);
        clear(YELLOW);
        setPenColor(BLACK);
        line(0, 0, 0, 19);
        line(19, 19, 19, 0);
        line(0, 19, 19, 19);
        line(0, 0, 19, 0);
        for (double i = 0; i < 19; i++) {
            line(0.0, i, 19, i);
            line(i, 0.0, i, 19);
        }
        for (int x = 0; x < 19; x++) {
            for (int y = 0; y < 19; y++) {
                if (board[x][y] != YELLOW) {
                    setPenColor(board[x][y]);
                    filledCircle(x, y, 0.47);
                    setPenColor(GRAY);
                    circle(x, y, 0.47);
                }
            }
        }
        int h = 0;

    }

    public static void main(String[] args) {
        int px;
        int py;
        Color[][] temp = new Color[19][19];
        Color[][] board = new Color[19][19];
        Color player = WHITE;
        for (int i = 0; i < 19; i++) {
            for (int h = 0; h < 19; h++) {
                board[i][h] = YELLOW;
                temp[i][h] = YELLOW;
            }
        }
        while (true) {
            drawGame(board);
            while (!mousePressed()) {

            }
            px = (int) round(mouseX());
            py = (int) round(mouseY());
            board[px][py] = player;
            while (mousePressed()) {

            }
            floodFill(px, py, player, board, temp);
            System.out.print("XXXXX = "+ temp[px][py]);
            if (checkTemp(temp, board, px, py)) {
                for (int x = 0; x < 19; x++) {
                    for (int y = 0; y < 19; y++) {
                        if (temp[x][y] == GRAY) {
                            board[x][y] = YELLOW;
                        }
                    }
                }
            }
            player = opposite(player);
        }
    }

    private static boolean checkTemp(Color[][] temp, Color[][] board, int x,
            int y) {
        if (x < 19 && x > -1 && y < 19 && y > -1) {
            if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW
                    || temp[x][y - 1] == YELLOW || temp[x][y + 1] == YELLOW) {
                return false;
            }
        }
        if (x == 18) {
            if (temp[x - 1][y] == YELLOW || temp[x][y - 1] == YELLOW
                    || temp[x][y + 1] == YELLOW) {
                return false;
            }
        }
        if (y == 18) {
            if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW
                    || temp[x][y - 1] == YELLOW) {
                return false;
            }
        }
        if (y == 0) {
            if (temp[x + 1][y] == YELLOW || temp[x - 1][y] == YELLOW
                    || temp[x][y + 1] == YELLOW) {
                return false;
            }
        }
        if (x == 0) {
            if (temp[x + 1][y] == YELLOW || temp[x][y - 1] == YELLOW
                    || temp[x][y + 1] == YELLOW) {
                return false;
            }
        }

        else {
            if (x < 19) {
                if (temp[x + 1][y] == GRAY) {
                    checkTemp(temp, board, x + 1, y);
                }
            }
            if (x >= 0) {
                if (temp[x - 1][y] == GRAY) {
                    checkTemp(temp, board, x - 1, y);
                }
            }
            if (y < 19) {
                if (temp[x][y + 1] == GRAY) {
                    checkTemp(temp, board, x, y + 1);
                }
            }
            if (y >= 0) {
                if (temp[x][y - 1] == GRAY) {
                    checkTemp(temp, board, x, y - 1);
                }
            }
        }
        return true;
    }

    private static void floodFill(int x, int y, Color player, Color[][] board,
            Color[][] temp) {
        if (board[x][y] != player) {
            return;
        } else {
            temp[x][y] = GRAY;
            System.out.println("x = " + x + " y = " + y);
            if (x < 19) {
                floodFill(x + 1, y, player, board, temp);
            }
            if (x >= 0) {
                floodFill(x - 1, y, player, board, temp);
            }
            if (y < 19) {
                floodFill(x, y + 1, player, board, temp);
            }
            if (y >= 0) {
                floodFill(x, y - 1, player, board, temp);
            }
        }
    }

}