Java Swing tutorials.
Swing.plaf, ScrollBarUI, ButtonUI etc which are present in UI delegates defines the accurate API which can be used by a component for interaction with instance of UI delegate. It shall be noted that originally interfaces were used here but got replaced by abstract classes as it was being felt that API was immature to with-stand interface’s concrete casting. Implementation of look and feel’s root is plaf APIs.
Every implementation of look and feel gives abstract plaf classes’s concrete