Drawing Lots Of Markers On A Map

I'm trying to draw on a map using markers. The problem I'm having is when I try to add lots of them, then I can't get it to run. To illustrate my problem, let's say I want to draw a square made of 900 smaller squares (30x30).I'm trying to add the markers to an itemizedoverlay, then drawing it.

Code:
public class MyItemizedOverlay extends ItemizedOverlay{
private ArrayList<OverlayItem> mOverlays = new ArrayList<OverlayItem>();
private Context mContext;
[code]....