Recoverable applications - Software Development Case Studies in Java - page 490

public Trackable cloneTarget() {
Tower clone # new Tower();
clone.restore( this );
return clone;
}
public String toString() {
String result # "";
for ( int i # 0; i < 10; i !! )
result !# queue[i] ! " ";
return result;
}
}
Class Hanoi represents a complex recoverable object, i.e. the container of
the three Tower objects. Method move() causes a state transition and thus its
invocations must be registered.
public class Hanoi implements Trackable {
Tower[] towers # new Tower[3];
DrawingArea drawingArea # null ;
public void init() {
try {
towers[0] # new Tower();
towers[1] # new Tower();
towers[2] # new Tower();
towers[0].init(10);
// registers the three Tower objects with three
// different labels
Tracker.bind(towers[0], "tower_1");
Tracker.bind(towers[1], "tower_2");
Tracker.bind(towers[2], "tower_3");
}
catch (Exception e) { e.printStackTrace(); }
}
// moves a disc between two pegs
public void move(String from, String to) {
int f # towers[Integer.parseInt(from)].sizeOfFirst();
int t # towers[Integer.parseInt(to)].sizeOfFirst();
if (f > # t && t ! # 0)
return ;
// records the state of this object before
// the execution of method move()
Tracker.record( this , "move", Tracker.BEFORE);
towers[Integer.parseInt(to)].push(
towers[Integer.parseInt(from)].pull() );
drawingArea.drawingPanel.repaint();
// records the state of this object after
// the execution of method move()
Tracker.record( this , "move", Tracker.AFTER);
}