code: public Class<?> findClass(String className)
  	{
  	
  		Class<?> result = null;
  
  		// look in hash map
  		result = (Class<?>) classes.get(className);
  		if (result != null)
  		{
  			return result;
  		}
  
  		try
  		{
  			return findSystemClass(className);
  		}
  		catch (Exception e)
  		{
  			Debugger.printWarn(e);
  		}
  
  		try
  		{
  			URL resourceURL = ClassLoader.getSystemResource(className.replace(
  					'.', File.separatorChar) + ".class");
  
  			if (resourceURL == null)
  				return null;
  
  			String classPath = resourceURL.getFile();
  
  			classPath = classPath.substring(1);
  
  			return loadClass(className, new File(classPath));
  		}
  		catch (Exception e)
  		{
  			Debugger.printError(e);
  			return null;
  		}
  	}
docs: Find the class by it name
  
  @param className  the class name
  @return the existing of loaded class