#9_Methods and Containment in Unions_17_v3.ppt

Java template for Entrypublic class Entry { private Date date; private double distance; private int durationInMinutes; private String postRunFeeling; public EntryDate date, double distan

Methods and Containment in Unions

Week 9, 10

HOW TO DESIGN CLASS

HIERARCHIES

Basic Java Programming

Course material developed by Mai Anh Tho (tho@hcmuaf.edu.vn)

Managing a Runner’s Logs

Example

Recall the problem of tracking a

runner’s workouts

• Develop a program that manages a

runner's training log Every day the runner enters one entry concerning the day's

run .For each entry, the program should compute how fast the runner ran (Exercise 3.1.4 & 3.1.5 in week 1) .The runner

may also wish to determine the total

number of miles run

• Draw a class diagram for a runner’s log

Class diagram for a runner’s log

Add methods to the runner’s log

- ALog rest + ??? nnn(??)

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• Write Java method templates for all the classes in the class diagram

Java template for Date

this day = day;

this month = month;

this year = year;

Java template for Entry

public class Entry {

private Date date;

private double distance;

private int durationInMinutes;

private String postRunFeeling;

public Entry(Date date, double distance, int durationInMinutes, String postRunFeeling) {

this date = date;

this distance = distance;

this durationInMinutes = durationInMinutes;

this postRunFeeling = postRunFeeling;

Java template for ALog

}

Java template for MTLog

Java template for ConsLog

this first = first;

this rest = rest;

• Give some examples for a runner’s log How many examples are at least needed?

Examples for a runner’s log

Date d1 = new Date(5, 5, 2005);

Date d2 = new Date(6, 6, 2005);

Date d3 = new Date(23, 6, 2005);

Entry e1 = new Entry(d1, 5.0, 25, "Good");

Entry e2 = new Entry(d2, 3.0, 24, "Tired");

Entry e3 = new Entry(d3, 26.0, 156, "Great");

Alog l1 = new MTLog();

Alog l2 = new ConsLog(e1,l1);

Alog l3 = new ConsLog(e2,l2);

Alog l4 = new ConsLog(e3,l3);

• Using the method template for ALog, design a method to compute the total number of miles run

miles() for ALog

// to compute the total number of miles recorded in this log

}

• Develop some examples to test the miles() method

Examples to test miles()

Date d1 = new Date(5, 5, 2005);

Date d2 = new Date(6, 6, 2005);

Date d3 = new Date(23, 6, 2005);

Entry e1 = new Entry(d1, 5.0, 25, "Good");

Entry e2 = new Entry(d2, 3.0, 24, "Tired");

Entry e3 = new Entry(d3, 26.0, 156, "Great");

ALog l1 = new MTLog();

ALog l2 = new ConsLog(e1, l1);

ALog l3 = new ConsLog(e2, l2);

ALog l4 = new ConsLog(e3, l3);

l1.miles()  should be 0.0

l2.miles()  should be 5.0

l3.miles()  should be 8.0

l4.miles()  should be 34.0

• Implement miles() in MTLog and ConsLog

miles() in ConsLog

public class ConsLog extends ALog {

private Entry first;

private ALog rest;

public ConsLog(Entry first, ALog rest) {

this first = first;

this rest = rest;

}

public double miles() {

return this first.getDistance() + this rest.miles(); }

}

getDistance() in Entry

public class Entry {

private Date date;

private double distance;

private int durationInMinutes;

private String postRunFeeling;

…

public double getDistance() {

return this distance;

}

}

Extension of the runner’s log problem

• The runner wants to see his log for a

• Q: Design a method to fulfill this

requirement in ALog

getLog() for ALog

public abstract class ALog {

// to compute the total number of miles recorded in this log

public abstract double miles();

// to extract those entries in this log for the given month and year

public abstract ALog getLog( int month, int year);

}

• Develop some examples to test the getLog() method

Examples to test getLog()

Date d1 = new Date(5, 5, 2005);

Date d2 = new Date(6, 6, 2005);

Date d3 = new Date(23, 6, 2005);

Entry e1 = new Entry(d1, 5.0, 25, "Good");

Entry e2 = new Entry(d2, 3.0, 24, "Tired");

Entry e3 = new Entry(d3, 26.0, 156, "Great");

Alog l1 = new MTLog();

Alog l2 = new ConsLog(e1,l1);

Alog l3 = new ConsLog(e2,l2);

Alog l4 = new ConsLog(e3,l3);

l1.getLog(6,2005)  should be new MTLog()

l2.getLog(6,2005)  should be new MTLog()

l3.getLog(6,2005)  should be new ConsLog(e2, new MTLog()) l3.getLog(5,2005)  should be new ConsLog(e1, new MTLog()

getLog() for MTLog

public class MTLog extends ALog {

public MTLog() { }

public double miles() {

return 0.0;

}

public ALog getLog( int month, int year) {

return new MTLog();

}

}

getLog() for ConsLog

public class ConsLog extends ALog {

private Entry first;

private ALog rest;

public ConsLog(Entry first, ALog rest) {

this first = first;

this rest = rest;

}

public double miles() {

return this first.getDistance() + this rest.miles();

sameMonthInAYear() in Entry

public class Entry {

private Date date;

private double distance;

private int durationInMinutes;

private String postRunFeeling;

…

public double getDistance() {

return this distance;

}

// was this entry made in the given month and year

public boolean sameMonthInAYear(int month, int year) {

return ( this date.sameMonthInAYear(month, year); }

}

sameMonthInAYear() in Date

private int day;

private int month;

private int year;

public Date(int day, int month, int year) {

this day = day;

this month = month;

this year = year;

}

return (this.month == month) && (this.year == year);

}

}

ALog class diagram

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ALog

<<abstract>> double miles()

<<abstract>> ALog getLog(int month, int year)

<<abstract>>

ConsLog

- Entry first

- ALog rest + double miles() + ALog getLog(int month, int year)

11 11

Exercises

Exercise 6.1.1

• Collect all the pieces of getLog() and

insert the method definitions in the class hierarchy for logs Develop examples for

sameMonthInAYear() and include them

with the test suite Draw the class diagram for this hierarchy

Exercise 6.1.2

• Suppose the requirements for the program that tracks a runner's log includes this

request:

The runner wants to know the total

Design the method that computes this

number and add it to the class hierarchy of exercise 6.1.1

Exercise 6.1.3

• Suppose the requirements for the program that tracks a runner's log includes this request:

A runner wishes to know the maximum

distance ever run .

Design the method that computes this number and add it to the class hierarchy of

exercise 6.1.1

Assume that the method produces 0 if the log is empty.

Sorting Example

Problem Statement

The runner would like to see the log with entries ordered according to the distance covered in each run, from the shortest to the longest distance

• Q: Which class should this operation

belong to?

sortByDistance() in ALog

public abstract class ALog {

// to create from this log a new log with entries sorted by distance

public abstract ALog sortByDistance();

}

Date d1 = new Date(5, 5, 2005);

Date d2 = new Date(6, 6, 2005);

Date d3 = new Date(23, 6, 2005);

Entry e1 = new Entry(d1, 5.0, 25, "Good");

Entry e2 = new Entry(d2, 3.0, 24, "Tired");

Entry e3 = new Entry(d3, 26.0, 156, "Great");

Alog l1 = new MTLog();

Alog l2 = new ConsLog(e1,l1);

Alog l3 = new ConsLog(e2,l2);

Alog l4 = new ConsLog(e3,l3);

l1.sortByDistance()  should be l1

l2.sortByDistance()  should be l2

l4.sortByDistance()  should be new ConsLog(e2,

new ConsLog(e1, new ConsLog(e3, new MTLog()))

}

sortByDistance() in ConsLog

public class ConsLog extends ALog {

private Entry first;

private ALog rest;

• Which class should insertInDistanceOrder()

operation belong to?

<<abstract>> + ALog sortByDistance()

<<abstract>> ALog insertInDistanceOrder(Entry)

insertInDistanceOrder() in ALog

public abstract class ALog {

// to create from this log a new log with entries sorted by distance

public abstract ALog sortByDistance ();

// insert the given entry into this sorted log

public abstract ALog insertInDistanceOrder (Entry e);

}

Examples for insertInDistanceOrder()

ALog l5 = new ConsLog(new Entry(new Date(1,1,2005), 25, 4.9, "good"),

new ConsLog(new Entry(new Date(1,2,2005), 26, 4.9, "okay"), new MTLog()))

l5.insertInDistanceOrder(new Entry(new Date(1,3,2005), 25.5, 4.9, "great"))

// should be

new ConsLog(new Entry(new Date(1,1,2005), 25 , 4.9, "good"),

new ConsLog(new Entry(new Date(1,3,2005), 25.5, 4.9, "great"),

new ConsLog(new Entry(new Date(1,2,2005), 26 , 4.9, "okay"), new MTLog())))

l5.insertInDistanceOrder(new Entry(new Date(1,4,2005), 4.9, 26.5, "all right!"))

// should be

new ConsLog(new Entry(new Date(1,1,2005), 25 , 4.9, "good"),

new ConsLog(new Entry(new Date(1,2,2005), 26 , 4.9, "okay"),

new ConsLog(new Entry(new Date(1,4,2005), 26.5, 4.9, "all right!"), new MTLog())))

l5.insertInDistanceOrder(new Entry(new Date(1,5,2005), 24.0, 4.9, "bad"))

// should be

new ConsLog(new Entry(new Date(1,5,2005), 24.0, 4.9, "bad")

new ConsLog(new Entry(new Date(1,1,2005), 25 , 4.9, "good"), new ConsLog(new Entry(new Date(1,2,2005), 26 , 4.9, "okay"), , new MTLog())))

protected ALog insertInDistanceOrder(Entry e) {

return new ConsLog(e, this );

}

}

insertInDistanceOrder() in ConsLog

public class ConsLog extends ALog {

private Entry first;

private ALog rest;

…

public ALog sortByDistance() {

return this rest.sortByDistance().insertInDistanceOrder( this first);

}

protected ALog insertInDistanceOrder(Entry e) {

if (e hasDistanceShorterThan ( this first))

return new ConsLog(e, this );

else

return new ConsLog( this first, this rest.insertInDistanceOrder(e)); }

}

hasDistanceShorterThan() in Entry

public class Entry {

private Date date;

private double distance;

private int durationInMinutes;

private String postRunFeeling;

…

public boolean hasDistanceShorterThan(Entry entry) {

return this distance < entry.distance;

}

}

Exercises

6.2.1 Exercise

• Suppose the requirements for the program that tracks a runner’s log includes this

request:

The runner would like to see the log with

entries ordered according to the pace

from the fastest to the slowest

Design this sorting method Hint: Don’t forget to design methods for auxiliary tasks.

Overlapping Shapes Example

Remind The Problem

• Develop a drawing program that deals with at least three kinds of shapes: dots, squares, and circles .In addition, the program should also deal with overlaying shapes on each other In the following figure, for example, we have superimposed a circle on the right side of a square:

• We could now also superimpose(thêm vào) this

compounded shape on another shape and so on

Recall the current design

CartesianPoint

- int x

- int y + int getX() + int getY() + double distanceToO() + double distanceTo(CartesianPoint that) + void translate(int dx, int dy)

AShape

# CartesianPoint location

# AShape(CartesianPoint location) + double distanceToO()

+ double area() + boolean contains(CartesianPoint point) + Rectangle boundingBox()

Design 1

CartesianPoint

- int x

- int y + int getX() + int getY() + double distanceToO() + double distanceTo(CartesianPoint that) + void translate(int dx, int dy)

Design 2

CartesianPoint

- int x

- int y + int getX() + int getY() + double distanceToO() + double distanceTo(CartesianPoint that) + void translate(int dx, int dy)

+ double distanceTo(CartesianPoint that)

+ void translate(int dx, int dy)

+ double area() + boolean contains(CartesianPoint point) + Rectangle boundingBox()

AShape + double distanceToO() 22

• Q: Which design do you prefer?

• A: I prefer Design 4 Why?

– Design 1 has an EmptyShape, but in this case a shape (regardless being composite or not) is

always non-empty

– Design 2 has a flaw: there is no explicit end (of course you could use null)

– For Design 3, when having the new class

Composite I just have to change a class name

and add some classes more without changing the current design

AShape s1 = new Square( new CartesianPoint(4, 3), 40); AShape s2 = new Square( new CartesianPoint(3, 4), 50); AShape c1 = new Circle( new CartesianPoint(0, 0), 20); AShape c2 = new Circle( new CartesianPoint(12, 5), 20); AShape u1 = new CompositeShape(s1, s2);

AShape u2 = new CompositeShape(s1, c2);

AShape u3 = new CompositeShape(c1, u1);

AShape u4 = new CompositeShape(u3, u2);

}

}

The user wishes to know how close a combination of shapes is

to the origin

Modified Class Diagram

+ double distanceTo(CartesianPoint that)

+ void translate(int dx, int dy)

+ double area() + boolean contains(CartesianPoint point) + Rectangle boundingBox()

AShape + double distanceToO() 22

distanceToO() in CompositeShape

this top = top;

this bottom = bottom;

}

this bottom.distanceToO());

}

}

Problem 2

Add a method that determines

whether some point in the Cartesian space falls within the boundaries of some shape .

CartesianPoint location ASingleShape(CartesianPoint location) double distanceToO()

double area() boolean contains(CartesianPoint point)

opname()

Rectangle boundingBox() double perimeter()

Dot Square

int size

Circle int radius

Rectangle int width int height

double distanceTo(CartesianPoint that)

void translate(int dx, int dy)

11

AShape double distanceToO() boolean contains(CartesianPoint point)

CompositeShape AShape top

AShape bottom double distanceToO() boolean contains(CartesianPoint point)

22

Modified Class Diagram

contains() in CompositeShape

this top = top;

this bottom = bottom;

}

…

this bottom.contains(point);

}

}

Problem 3

A graphics program must

compute the bounding box for a shape

Bounding box for Composite shape

Y

a b

c

c r

(x1, y1)

(x2, y2)

(x3, y3) (x1+a, y1+b)

(x3+c, y3+c)

boundingBox() in CompositeShape

this top = top;

this bottom = bottom;

River Systems Example

m(7, 5) a(5, 5)

u(3, 7)

t(1, 5) s(1, 1)

b(3, 3)

Confluence

Source

Class Diagram (Version 1)

11

• Q: Which version do you prefer, Version 1

or Version 2? Why?

• The previous designs need to be modified

in case that a confluence may be made

from more than two streams

Problem 1

The EPA must represent river systems and monitor them…An EPA officer may wish to query a computer about the number of

sources that feed a river system…

Problem 2

An EPA officer may wish to find out

whether some location is a part of a river

system, regardless of whether it is a source, a confluence, or the river mouth .

Problem 3

An EPA officer may request the

number of miles of a river system,

either starting from the river's mouth or any of its confluence points .

Exercises

Exercise 6.5.1

Design a data representation for shopping lists Start from the class of grocery items developed in exercise 5.1.2 Add the following methods:

• howMany, which computes the number of items

on the shopping list;

• brandList, which produces the list of all brand names; and

• highestPrice, which determines the highest unit price among all items in the shopping list.

Exercise 5.1.2 Class Diagram

AnItem # String branchName # double weight # double price + double unitPrice() + boolean lowerPrice(double amount) + boolean cheaperThan(AnItem that)()