BlockBreakEvent

@EventHandler
public void onBlockBreak(BlockBreakEvent event)
{
  SpoutBlock BlockDestroy = (SpoutBlock) event.getBlock();
  Location loc = new Location(BlockDestroy.getWorld(),BlockDestroy.getX(),BlockDestroy.getY()+1,BlockDestroy.getZ());
  SpoutBlock BlockAbove = (SpoutBlock) loc.getBlock();

  if(BlockDestroy.isCustomBlock() && BlockAbove.isCustomBlock())
  {
    CustomBlock CustomBlockDestroy = BlockDestroy.getCustomBlock();
    CustomBlock CustomBlockAbove = BlockAbove.getCustomBlock();

    if( CustomBlockDestroy.getClass() == me.bootscreen.customslabs.slabs.BookshelfSlab.class &&
        CustomBlockAbove.getClass() == me.bootscreen.customslabs.slabs.BookshelfSlab.class)
    {
      System.out.print("Clear Drop");
      event.getBlock().getDrops().clear();
    }
  }
}