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public interface EventTarget {

public void performEvent (EventObject e);

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public class EventConnector {

// There are zero or more targets represented as a vectorprivate Vector targets = new Vector();

// When the source raises an event, the “performEvent”// method of each target is invokedpublic void raiseEvent (EventObject e) {

for (int i=0; i<targets.size(); i++) {EventTarget t = (EventTarget) targets.elementAt (i);t.performEvent (e);

}}

// Each target must register itself as a target of// this connector. Targets are simply added to the// “targets” vector.public void connectAsTarget (EventTarget targetComponent) {

targets.add (targetComponent);}

}

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// Target implements this method. It is called by the

// event connector whenever a new event is fired.

public interface EventTarget {

public void performEvent (EventObject e);

}

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public interface EventTarget {

public void performEvent (EventObject e);

}

// This class implements the EventTarget interface. This class// can contain any fields and methods, but must include an// an implementation of the performEvent method

public class HandleEvent implements EventTarget {

...

public void performEvent (EventObject e) {

System.out.println (“Got event ” + e);

}

...

}

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class CaptureLines implements MouseListener { private EventConnector e; private Point lastPoint = null; JFrame frame;

public void mouseClicked(MouseEvent mevt) {Point newPoint = mevt.getPoint();if (lastPoint == null) { lastPoint = newPoint;} else { LineEvent levt =

new LineEvent ( this, lastPoint, newPoint);

lastPoint = newPoint;

e.raiseEvent (levt);}

} ...

class CaptureLines implements MouseListener { ...

public CaptureLines (EventConnector e) {this.e = e;

JFrame frame = new JFrame("FrameDemo");

frame.addMouseListener (this);frame.setSize (500, 400);frame.setVisible (true);

}}

// Records lines into a list of lines

public class Lines implements EventTarget { // The lines that have been added private Vector lines = new Vector();

// Add a new line into the list of lines public void performEvent (EventObject e) {

lines.add (e); }

// Return the list of lines public Vector getLines() {

return lines; }}

import java.util.EventObject;import java.awt.Point;

// Simply traces events as they occur.

public class Trace implements EventTarget { public void performEvent (EventObject e) {

LineEvent nextLine = (LineEvent) e;Point p1 = nextLine.getSourcePoint();Point p2 = nextLine.getTargetPoint();

System.out.println ("Got line: " + "(" + Math.round(p1.getX())

+ "," + Math.round (p1.getY()) + ")" + "->" + "(" + Math.round(p2.getX()) + ",”

+ Math.round(p2.getY()) + ")" ); }}

import java.util.EventObject;import java.awt.Point;

public class LineEvent extends EventObject { private Point sourcePoint; private Point targetPoint;

public Point getSourcePoint () {return sourcePoint;

}

public Point getTargetPoint () {return targetPoint;

}

public LineEvent (Object source, Point sourcePoint, Point targetPoint) {

super(source);this.sourcePoint = sourcePoint;this.targetPoint = targetPoint;

}}

import java.util.EventObject;

// Target implements this method. It is called by the// event connector whenever a new event is fired.

public interface EventTarget { public void performEvent (EventObject e);}

import java.util.Vector;import java.util.EventObject;

public class EventConnector { private Vector targets = new Vector();

public void raiseEvent (EventObject e) {for (int i=0; i<targets.size(); i++) { EventTarget t =

(EventTarget) targets.elementAt (i); t.performEvent (e);}

}

public void connectAsTarget ( EventTarget targetComponent) {

targets.add (targetComponent); }}

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class CaptureLines implements MouseListener, EventTarget {private EventConnector e;

... public void performEvent (EventObject e) {

LineEvent nextLine = (LineEvent) e;

Graphics g = frame.getGraphics();

// Extract the points of the line from the event Point p1 = nextLine.getSourcePoint(); Point p2 = nextLine.getTargetPoint();

int x1=(int)Math.round (p1.getX());int y1=(int)Math.round (p1.getY());int x2=(int)Math.round (p2.getX());int y2=(int)Math.round (p2.getY());

// Draw the line in the windowg.drawLine (x1, y1, x2, y2);

}...

}

public class Main { public static void main(String[] args) {

// Create the connectorEventConnector ec = new EventConnector();

// Create the line event generatorCaptureLines captureComponent = new CaptureLines (ec);...// The third target is the line generator itselfec.connectAsTarget (captureComponent);

}}

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6XSSRUW�6HFRQG�:LQGRZpublic class Main { public static void main(String[] args) {

// Create the connectorEventConnector ec = new EventConnector();

// Create the line event generatorCaptureLines captureComponent = new CaptureLines (ec);...// The third target is the line generator itselfec.connectAsTarget (captureComponent);

// And let's create another window - we can draw lines there// as well!CaptureLines anotherCaptureComponent = new CaptureLines (ec);ec.connectAsTarget (anotherCaptureComponent);

}}

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class CaptureLines implements MouseListener, EventTarget { ... JFrame frame;

public CaptureLines (EventConnector e) {...// Create a window in which a user can clickframe = new JFrame("Useless Drawing Program");...// Adds this object as a target for mouse events// generated in this window. This method requires// an object of type MouseListener . frame.addMouseListener (this);...

}}

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// Generates a mouse click eventvoid mouseClicked(MouseEvent e)

// Generates an event when the mouse moves over the componentvoid mouseEntered(MouseEvent e)

// Generates an event when the mouse moves off the componentvoid mouseExited(MouseEvent e)

// Generates an event when a mouse button is depressedvoid mousePressed(MouseEvent e)

// Generates an event when a mouse button is releasedvoid mouseReleased(MouseEvent e)

class CaptureLines implements MouseListener, EventTarget { ...

public void mouseClicked(MouseEvent mevt) {Point newPoint = mevt.getPoint();if (lastPoint == null) { // This is the first click - record this point lastPoint = newPoint;} else { // Create a line event recording a line from the last point // to this new point, then record the new point. LineEvent levt = new LineEvent (this, lastPoint, newPoint); lastPoint = newPoint;

// Fire the event e.raiseEvent (levt);}

}

// These are other mouse events that may arise; we ignore these public void mouseEntered(MouseEvent e) {} public void mouseExited(MouseEvent e) {} public void mousePressed(MouseEvent e) {} public void mouseReleased(MouseEvent e) {}

...}