物事を非常にシンプルに保つことができるように思えます。
私の理解
その場合は、両方のイベントを処理する必要があります ( A の基本と B の基本+特定)
そのためにメソッドをオーバーロードする必要はありません。必要なのは、特定のイベントに対して特定のハンドラー (またはリスナー) を追加することだけです。
イベントが「基本」である場合もありますが、それで問題ありません。
ただし、イベントが特定の場合は、それに応じて対応する必要があります。したがって、特定のリスナーにチェックを追加して、次のように特定のイベントを識別します。
if( whichEvent instanceof SpecificEvent ) {
SpecificEvent s = ( SpecificEvent ) whichEvent;
// Do something specific here...
}
以上です。
問題の説明が抽象的すぎるため、具体的な解決策が提案されない場合があります。それでも、達成したいことを説明するのが難しい場合は、最初に問題が何であるかを再分析する必要があるでしょう。
上記の私の理解が正しければ（基本的なものと特定のものを何度か処理する必要がある）、以下の長いコードが役立つ場合があります。
よろしくお願いします
import java.util.*;
class A {
// All the listener will be kept here. No matter if basic or specific.
private List<Listener> listeners = new ArrayList<Listener>();
public void add( Listener listener ) {
listeners.add( listener );
}
public void remove( Listener listener ) {
listeners.remove( listener );
}
// In normal work, this class just perform a basic operation.
public void normalWork(){
performBasicOperation();
}
// Firing is just firing. The creation work and the
// operation should go elsewhere.
public void fireEvent( Event e ) {
for( Listener l : listeners ) {
l.eventHappened( e );
}
}
// A basic operation creates a basic event
public void performBasicOperation() {
Event e = new BasicEvent();
fireEvent( e );
}
}
// Specialized version of A.
// It may perform some basic operation, but also under some special circumstances
// it may perform an specific operation too
class B extends A {
// This is a new functionality added by this class.
// Hence an specifi event is fired.
public void performSpecificOperation() {
Event e = new SpecificEvent();
// No need to fire in different way
// an event is an event and that's it.
fireEvent( e );
}
// If planets are aligned, I will perform
// an specific operation.
public void normalWork(){
if( planetsAreAligned() ) {
performSpecificOperation();
} else {
performBasicOperation();
}
}
private boolean planetsAreAligned() {
//return new Random().nextInt() % 3 == 0;
return true;
}
}
// What's an event? Something from where you can get event info?
interface Event{
public Object getEventInfo();
}
// This is the basic event.
class BasicEvent implements Event{
public Object getEventInfo() {
// Too basic I guess.
return "\"Doh\"";
}
}
// This is an specific event. In this case, an SpecificEvent IS-A BasicEvent.
// So , the event info is the same as its parent. "Doh".
// But, since this is an SpecificEvent, it also has some "Specific" features.
class SpecificEvent extends BasicEvent {
// This method is something more specific.
// There is no need to overload or create
// different interfaces. Just add the new specific stuff
public Object otherMethod() {
return "\"All I can say is , this was an specific event\"";
}
}
// Hey something just happened.
interface Listener {
public void eventHappened( Event whichEvent );
}
// The basic listner gets information
// from the basic event.
class BasicEventListener implements Listener {
public void eventHappened( Event e ) {
System.out.println(this.getClass().getSimpleName() + ": getting basic functionality: " + e.getEventInfo());
}
}
// But the specific listner may handle both.
// basic and specific events.
class SpecificListener extends BasicEventListener {
public void eventHappened( Event whichEvent ) {
// Let the base to his work
super.eventHappened( whichEvent );
// ONLY if the event if of interest to THIS object
// it will perform something extra ( that's why it is specific )
if( whichEvent instanceof SpecificEvent ) {
SpecificEvent s = ( SpecificEvent ) whichEvent;
System.out.println(this.getClass().getSimpleName() + ": aaand getting specific functionality too: " + s.otherMethod() );
// do something specific with s
}
}
}
// See it run.
// Swap from new A() to new B() and see what happens.
class Client {
public static void main( String [] args ) {
A a = new B();
//A a = new A();
a.add( new BasicEventListener() );
a.add( new SpecificListener() );
a.normalWork();
}
}
出力例:
BasicEventListener: getting basic functionality: "Doh"
SpecificListener: getting basic functionality: "Doh"
SpecificListener: aaand getting specific functionality too: "All I can say is , this was an specific event"
さらに、インターフェイスを削除してシンプルにすることもできます