Sooner or later, a writer will have the essential elements of formal sentence correctness under control and will want to find the best ways of making sentences convey meaning effectively: how to phrase statements definitely, place coordinate thoughts in coordinate structures, subordinate to sharpen the relation between main assertions and modifying elements, eliminate unnecessary words, vary sentence structure, maintain consistency of tone , and smooth the general flow of words. Seemingly minor improvements—the moving of a clause from one position to another, a shift from the passive to the active voice , even a slight change in rhythm—can make the difference between drab sentences and pointed ones. 
The other two listener types are part of the Swing components' conformance to the JavaBeans specification. Among other things, this means that Swing components support bound and constrained properties and notify listeners of changes to the properties. Property change listeners listen for changes to bound properties and are used by several Swing components, such as formatted text fields , to track changes on a component's bound properties. Also, property change listeners, as well as vetoable change listeners are used by builder tools to listen for changes on constrained properties. For more information refer to the Properties lesson in the JavaBeans trail.