Java Tile Based Random Terrain Generation

I have been working on a randomly tile based generation system for a game I am making in Java Eclipse. I have looked up a lot of videos and tutorials, but none of them fit my needs. I finally came up with a script that allows just that, but I am having trouble with importing textures instead of solid colors, and I am also having trouble with the checking system. The checking system I am trying to do will essentially check the squares around it and there be a X% chance that it will spawn its tile next to it and with a B% that it will spawn a different tile and so on. How should I go about this? Thank you for your time. `public class Map {

public static final Color CITY = new Color(214,217,223);
public static final Color DESERT = new Color(255,204,102);
public static final Color DIRT_ROAD = new Color(153,102,0);
public static final Color FOREST = new Color(0,102,0);
public static final Color HILLS = new Color(51,153,0);
public static final Color LAKE = new Color(0,153,153);
public static final Color MOUNTAINS = new Color(102,102,255);
public static final Color OCEAN = new Color(0,0,153);
public static final Color PAVED_ROAD = new Color(51,51,0);
public static final Color PLAINS = new Color(102,153,0);

public static final Color[] TERRAIN = {
    CITY,
    DESERT,
    DIRT_ROAD,
    FOREST,
    HILLS,
    LAKE,
    MOUNTAINS,
    OCEAN,
    PAVED_ROAD,
    PLAINS
};

public static final int NUM_ROWS = 25;
public static final int NUM_COLS = 30;

public static final int PREFERRED_GRID_SIZE_PIXELS = 60;

// In reality you will probably want a class here to represent a map tile,
// which will include things like dimensions, color, properties in the
// game world.  Keeping simple just to illustrate.
private final Color[][] terrainGrid;

public Map(){
    this.terrainGrid = new Color[NUM_ROWS][NUM_COLS];
    Random r = new Random();
    // Randomize the terrain
    for (int i = 0; i < NUM_ROWS; i++) {
        for (int j = 0; j < NUM_COLS; j++) {
            int randomTerrainIndex = r.nextInt(TERRAIN.length);
            Color randomColor = TERRAIN[randomTerrainIndex];
            this.terrainGrid[i][j] = randomColor;
        }
    }
    int preferredWidth = NUM_COLS * PREFERRED_GRID_SIZE_PIXELS;
    int preferredHeight = NUM_ROWS * PREFERRED_GRID_SIZE_PIXELS;
    setPreferredSize(new Dimension(preferredWidth, preferredHeight));
}

@Override
public void paintComponent(Graphics g) {
    // Important to call super class method
    super.paintComponent(g);
    // Clear the board
    g.clearRect(0, 0, getWidth(), getHeight());
    // Draw the grid
    int rectWidth = getWidth() / NUM_COLS;
    int rectHeight = getHeight() / NUM_ROWS;

    for (int i = 0; i < NUM_ROWS; i++) {
        for (int j = 0; j < NUM_COLS; j++) {
            // Upper left corner of this terrain rect
            int x = i * rectWidth;
            int y = j * rectHeight;
            Color terrainColor = terrainGrid[i][j];
            g.setColor(terrainColor);
            g.fillRect(x, y, rectWidth, rectHeight);
        }
    }
}

public static void main(String[] args) {
    // http://ift.tt/1pSUheb
    SwingUtilities.invokeLater(new Runnable() {

        @Override
        public void run() {
            // TODO Auto-generated method stub

        }

    });
}

}enter image description here