Interaction Diagrams

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Chapter 15

• Interaction Diagrams

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Most Common

• Sequence Diagram
• Communication Diagram
• Sequence Diagrams illustrate interactions between
  classes of a program using class methods as
  message names,

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Sample Code
public class A private B myB null
public A () myB new B()
public void doOne() myB.doTwo()
myB.doThree()
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Fig. 15.1
duration of doOne() activity
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Fig. 15.2
Communication Diagram
sequence numbers
Same interaction in a network diagram
description
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Strengths and Weaknesses

• UML has put more thought into SDs
• Better tool support for SDs
• Better at showing sequence
• CDs are more space efficient, boxes can go
  anywhere
• Easier to modify a CD
• CDs are vertical so fit on narrow pages of a
  book

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Fig. 15.3
lifeline
NOTE If you need to extend youve run out of
space
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Fig. 15.4
NOTE If you need to extend you can come back
to the left.
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Static vs Dynamic View

• The Class Diagram is a static view of the program
  while the Sequence Diagram is a dynamic view.
  Both are useful.

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Fig. 15.5
Common Notation
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Fig. 15.6
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Singleton Pattern

• http//en.wikipedia.org/wiki/Singleton_pattern

public class Singleton // Private
constructor suppresses // generation of a
(public) default constructor private
Singleton() private static class
SingletonHolder private static
Singleton instance new Singleton()
public static Singleton getInstance()
return SingletonHolder.instance

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Fig. 15.7
Messages
also activation bar
asynchronous with dashed lines
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Message Return Values

• Two ways to show the return result
• Using the message syntax
• returnVar message(parameter).
• Using a reply (or return) message line at the end
  of an activation bar

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Fig. 15.8
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Fig. 15.9
representing a message sent to the same object
not just to an object of the same class
this.clear()
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Fig. 15.10
New Object Creation
dashed line because UML says so
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Fig. 15.11
Im not sure where this fits in the Java paradigm?
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Fig. 15.12
more items
I think this notation is starting to get out of
hand. I, because I am drawing on the whiteboard,
would draw and arrow like I have.
In general, these are called diagram frames
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Fig. 15.13
I have no easy alternative to this except to not
bother trying to describe an entire algorithm.
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Diagram Frames
Frame Operator
Meaning
Alt Alternative fragment for mutual exclusion conditional logic expressed in the guards.
Loop Loop fragment while guard is true. Can also write loop(n) to indicate looping n times. There is discussion that the specification will be enhanced to define a FOR loop, such as loop(i, 1, 10)
Opt Optional fragment that executes if guard is true.
Par Parallel fragments that execute in parallel.
Region Critical region within which only one thread can run.
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Fig. 15.14
I like this better
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Fig. 15.15
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Fig. 15.16
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Sample Code
public class Sale private
ListltSalesLineItemgt lineItems new
ArrayListltSalesLineItemgt() public Money
getTotal() Money total new Money()
Money subtotal null for (
SalesLineItem lineItem lineItems )
subtotal lineItem.getSubtotal()
total.add( subtotal ) return total
//
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Fig. 15.17
An alternative for Figure 15.16 nothing is
official.
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Fig. 15.18
nested loops
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Fig. 15.19
sd sequence diagram
simplifies the first diagram
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Fig. 15.20
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Code Example
public class Foo public void doX()
// static method call on class Calendar
Locale locales Calendar.getAvailableLocales()
// //
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Fig. 15.21
abstract method call
individual implementations
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Fig. 15.22
asynchronous call
Guideline This arrow difference is subtle. And
when wall sketching UML, it is common to use a
stick arrow to mean a synchronous call because
it's easier to draw. Therefore, when reading a
UML interaction diagram don't assume the shape
of the arrow is correct!
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Code Example
public class ClockStarter public void
startClock() Thread t new Thread( new
Clock() ) t.start() //
asynchronous call to the 'run' method on the
Clock System.runFinalization()
// example follow-on message //
// objects should implement the Runnable
interface // in Java to be used on new threads
public class Clock implements Runnable
public void run() while ( true ) //
loop forever on own thread
// //
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Fig. 15.23
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Fig. 15.24
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Fig. 15.25
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Fig. 15.26
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Fig. 15.27
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Fig. 15.28
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Fig. 15.29
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Fig. 15.30
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Fig. 15.31
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Fig. 15.32
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Fig. 15.33
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Fig. 15.34
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Fig. 15.35