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Class programming101.calculBeanz.Calculator

java.lang.Object
    |
    +----FR.essi.sander.graphix.mvc.ModelImpl
            |
            +----programming101.calculBeanz.Calculator

public class Calculator
extends ModelImpl
implements ControlListener, Serializable

Defines a very simple calculator which combines a cumulative numeric value with a new numeric value according to some operation. The calculator as a whole rigorously applies the MVC (Model-View-Control) "design pattern", where the calculator state is the model (that's this component), the various buttons provide the control, and the display region is the display (really!). Communication is by way of events, e.g., the calculator (M component) registers itself as interested by button events (the C components), and when a button is pushed the appropriate event gets sent to the calculator which then calculates and posts an event to the display (the V component). This has the advantage of being modular, with each component in fact being a JavaBean.

This class

extends FR.essi.sander.graphix.mvc.ModelImpl
superclass supplies management for ModelListeners so we don't have to
implements FR.essi.sander.graphix.mvc.ControlListener
guarantees code for the update method which is invoked by control events
implements java.io.Serializable
needed for JavaBeans

Since:: 18/03/98
Version:: 1.2 (6/04/98)
Author:: © 1998 Peter T. Sander

Calculator(): No-args constructor (needed for JavaBeans).

getCumulator(): Getter method for cumulator attribute.
update(ControlEvent): Method guaranteed by implementing the ControlListener interface.

Calculator

public Calculator()

No-args constructor (needed for JavaBeans).

update

public void update(ControlEvent ce)

Method guaranteed by implementing the ControlListener interface. Invoked by any controls which have registered this calculator as interested by their events.

Parameters:: ce - a control button event
Overrides:: update in class ModelImpl

getCumulator

public double getCumulator()

Getter method for cumulator attribute.

Returns:: cumulator value

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