code: public boolean installed(Class<?> component) {
  		Preconditions.checkArgument(component != null, 
  				"Parameter 'component' must not be [" + component + "]");
  		return installed.contains(component);
  	}
docs: Indicates the specified component installed or not in the container.
  
  @param component The component class to be examined.
  @return <code>true</code> if the specified component installed in the
  container.