Problem drawing tiled image

Question

I have a tiled buffred image. I have implemented caching and tiling myself i.e. the complete image (that can be as big as 100+MB) is tiled into 512x512 tiles and i am keeping them in a cache implemented as hashmap. The cache size is adjusted based on the available memory.
My logic is that when the user scrolls the image i figure out the tiles that needed to be shown to the user and then see if i can find it in the cache, in case of a cache miss i create the tile in memory (using createCompatibleImage()). Once the tile is created i stuff it in my cache. After making sure the required tiles are available i then simply use drawImage(tile,x,y,null) to draw the tiles inside the paintComponent() method. My problem is that the tiles get drawn erratically i.e. if the viewport requires six tiles to be drawn then every so often few of the tiles do not get drawn. I have made sure that the my program does call drawImage() six times once for each tile - but it seems that despite drawImage call the actual drawing has a mind of its own.
I do not suspect my tile creation or cachig code since when someof the tiles are not shown properly all i have to do is to move mouse over the undrawn area and the tiles appear immediately.
My code is spread all over so it is difficult to produce all the relevant code in here, so i will give some code snippet:
// Code for creating a new tile
public createTile()
GraphicsConfiguration gc = Utility.getDefaultConfiguration();
BufferedImage overlayImage = gc.createCompatibleImage(width, height);
int ii = 0;
int jj = 0;
     for (int i= 0; i<width; i++){                
          for (int j=0; j<height; j++){
               int rgb = ....;//the rgb is calculated based on some specific logic.
               overlayImage.setRGB(ii,jj,rgb);
               jj++;
          ii++;
          jj = 0;
// After creating the image I then resize the image to handle zoom in/zoom out
// using nearest neighbor interpolation. I don't suspect the resize code so
// have not reporduce it here.
     return (resizeImage(overlayImage,newWidth,newHeight)).
====================================================
// Extract of some of my paint code is given below.
//I am not calling super.paintComponent() because i am redrawing the
// whole screen with my tiled image.
  public void paintComponent(Graphics g)
       Graphics2D g2d = (Graphics2D)g;
     Tile[]tiles = getChosenTiles();
               for (int i=0; i<tiles.length; i++){
                    g2d.drawImage(tiles.getImage(), tiles[i].x, tiles[i].y, null);

Answer 1

Since nobody replied to the post - i had no option but to dig into the problem myself. Good thing is that I managed to find the solution.
As it turned out my logic was as below:
Step 1: find out the tiles that need to be shown on the viewport.
Step 2: obtain these tiles from the cache
Step 2a: If tiles not found in cache then create the tiles in memory.
Step 3: for (int i=0;i<tiles.length; i++) {             
                g2d.drawImage(tiles.getImage(), null, tiles[i].x, tiles[i].y);
The problem was that for some reason the Java graphics drawing could not keep up with the for loop. What i did was to move the drawing logic inside Step 2. i.e. I would get a tile and then draw it immediately after getting it. In other words the logic was changed to
Step 1: find out the tiles that need to be shown on the viewport
Step 2:
             for (int i=0;i<tiles.length; i++) {
                 BufferedImage image = tiles.getImage();
if (image == null) {
image = createTileImage(tiles[i]);
tiles[i].setImage(image);
g2d.drawImage(tiles[i].getImage(), null, tiles[i].x, tiles[i].y);
This solved my problem.
-km