code: public <T extends Component> T getComponent (Class<T> componentClass) {
  		return getComponent(ComponentType.getFor(componentClass));
  	}
docs: Retrieve a component from this {@link Entity} by class. <em>Note:</em> the preferred way of retrieving {@link Component}s is
  using {@link ComponentMapper}s. This method is provided for convenience; using a ComponentMapper provides O(1) access to
  components while this method provides only O(logn).
  @param componentClass the class of the component to be retrieved.
  @return the instance of the specified {@link Component} attached to this {@link Entity}, or null if no such
  {@link Component} exists.