Object-Oriented Design and Programming II

CS262

Finite State Machines

Getting Oriented• Visit the class web page to access the syllabus, slides, handouts, and

grades. – http://www.uwosh.edu/faculty_staff/huen/262/s10262.htm

- Pick up code handouts from the shared drive on the Novell network (Soft Q drive): For example:

– Q:\Shared\Huen\262\Labs\S10_Labs

• Submit your work to the shared drive: For example: Q:\Shared\Huen\262\Submit\Lab01\

• Read the UWO Student Discipline Code (UWS 14) at – http://www.uwosh.edu/dean/conduct.htm

• Textbook companion site: http://cs.armstrong.edu/liang/intro6e/index.html (The contents of chapters 1 through 6 were covered in CS221)• BlueJ software documentation:

http://www.bluej.org/doc/documentation.html

Object-oriented analysis and design

For Thursday: Review chapter 7 of our textbook • Objects • Each object has a unique identity that

distinguishes it from every other object Examples: ceiling fan, subway turnstile, gumball machine, cruise control unit

• Objects have state and behaviors• What is the state of an object? • What do we mean by behavior?

Classes

• Similar objects are grouped in a single class – A class is a template or blueprint for all the objects

that share state and behavior. – More precisely, instances (or objects) of a class share

the same behaviors and the same set of states they could be in, but they have a different identity and (possibly) a different current state.

– UML diagrams are used to specify state, behaviors, classes, and more.

Finite-state machines

• A UML class diagram is static.• The UML also has several dynamic

models. – One of them is the FSM.

FSM = states + transitions (event/action)• Ceiling fan example:

Off Low

Pull/change speed Pull/changed speed

Med High

Pull/change speed

Pull/change speed

• A state-transition diagram is a visual representation of the logic of the FSM

Observation

One Java implementation of the ceiling fan example (Furcy)

Q:\Shared\Huen\262\LectureNotes\F09 Slides\week01

Output in pulling the cord 10 timesTurning slowlyTurning at medium speedTurning fastStopped turningTurning slowlyTurning at medium speedTurning fastStopped turningTurning slowlyTurning at medium speed

Discussion

Question: What will happen if you omit one of the break statements in CeilingFan.java?

Subway turnstile example

• (From Robert C. Martin, Engineering Notebook Column, June 98)

Locked Unlocked

Coin/unlock

turn/lock

Exercise: Implement this FSM for next time

Vending Machine Example

A control system has to control the amount of money dropped into a vending machine. To keep the example simple, let’s restrict the inputs: only 5 and 10 cent coins are accepted. The correct, recognized sum is 25 cents.

Start

Five

Ten

Fif-teen

Twen-ty

Stop

5

10

5

10

5

10

5

10

5

A State Machine Diagram for the vending machine counter

Table 1. Transition matrix for the vending machine counter. Inputs are in the cells

ToFrom

Start Five Ten Fifteen Twenty Stop

Start - 5 10 - - -

Five - - 5 10 - -

Ten - - - 5 10 -

Fifteen - - - - 5 10

Twenty - - - - - 5, 10/change

Stop - - - - - -

Alternative Form of the Transition MatrixTop row contains inputOther rows are states

InputState

5 10

Start Five Ten

Five Ten Fifteen

Ten Fifteen Twenty

Fifteen Twenty Stop

Twenty Stop Stop + change

Stop Stop Stop

A Gumball Machine• States

– No_quarter– Has_quarter– Sold– Sold-out

• Actions– Insert_quarter– Eject_quarter– Turn_crank– Dispense– Refill

Finite System Machine for Syllable Recognizer

Not in VG

In VG Vowel

Not vowel

Not vowel

Vowel / count++

Initial state

VG: Vowel Group

Cruise Control as a Finite State Machine

Controls:ON, OFF buttons.SET, (DEC, ACC) buttons.

Q0 ReadyCruiseON

ON

OFF

SET / set current speed

Brake

OFFOFF, SET,DEC, ACC/ null

How about “decelerate” and “accelerate”?