code: public static UnitConverter getCachedInstance(int pixelPerInch)
  	{
  		Integer _key = new Integer(pixelPerInch);
  		if (!theCache.containsKey(_key))
  		{
  			theCache.put(_key, new UnitConverter(pixelPerInch));
  		}
  		return theCache.get(_key);
  	}
docs: Retrieve from the cache, or create if not cached yet, a unit converter setted for the given pixel per inch value.
  
  @param pixelPerInch pixel per inch value.
  @return an instance tuned for the specified pixel density.