Duplicate code is something to be avoided. And yet, everyday developers make copies of working code, make edits to the copy, and create duplicate code. Some developers have the discipline and the skill to refactor to eliminate this duplicate code. Many do not.

1. The First 100 Hours:
Commonality and
Variability Analysis
Jason Cheong-Kee-You
@jpcky www.mightyjupiter.com
Alistair McKinnell
@amckinnell www.valuablecode.com

2. Commonality and
Variability Analysis

3. Commonality and
Variability Analysis
Avoiding Duplicate Code

4. Exercise

5. Exercise
1. Did you write any code last year?
If so, how many lines of code?
2. How many lines of code in your
code base?
3. Percentage of duplicate code?

6. Code Visibility

7. Code Visibility

8. Code Visibility

9. Avoiding Duplicate Code

10. Avoiding Duplicate Code

11. Avoiding Duplicate Code
DRY: Don’t Repeat Yourself

12. Avoiding Duplicate Code
DRY: Don’t Repeat Yourself
Every piece of knowledge must have
a single, unambiguous, authoritative
representation within a system.

13. Avoiding Duplicate Code

14. Avoiding Duplicate Code
Once and Only Once

15. Avoiding Duplicate Code
Once and Only Once
Data, structure, or logic should exist
in only one place in the system.

16. Avoiding Duplicate Code

17. Avoiding Duplicate Code
Test-Driven Development

18. Avoiding Duplicate Code
Test-Driven Development
1. Write new code only if an
automated test has failed.

19. Avoiding Duplicate Code
Test-Driven Development
1. Write new code only if an
automated test has failed.
2. Eliminate duplication.

20. Avoiding Duplicate Code

21. Avoiding Duplicate Code
Single Choice Principle

22. Avoiding Duplicate Code
Single Choice Principle
Whenever a software system must
support a set of alternatives, one
and only one module in the system
should know their exhaustive list.

23. Avoiding Duplicate Code

24. Avoiding Duplicate Code
Duplication may be the
root of all evil in software.

25. Exercise

26. Exercise

27. Exercise
What are the consequences of
duplicate code?

28. Exercise
What are the consequences of
duplicate code?
Consider both good and evil.

29. Exercise

30. Exercise

31. Exercise
How does duplicate code
come about?

32. Exercise
How does duplicate code
come about?
Make a Top 3 list.

34. Alistair’s Contention

35. Alistair’s Contention
Copy and Paste leads to the
creation of duplicate code.

36. Alistair’s Contention
Copy and Paste leads to the
creation of duplicate code.
Developers lack the thinking tools
and the development skills to avoid
the duplication.

37. Duplicate Code:
Select Options

38. Select Options
public static List<SelectOption> createEndMonthList(Date expiryDate) {
List<SelectOption> monthList = new ArrayList<SelectOption>();
int month = getDateMonth(expiryDate);
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(true);
} else {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(false);
}
monthList.add(option);
}
return monthList;
}

39. Select Options
public static List<SelectOption> createEndMonthList(Date expiryDate) {
List<SelectOption> monthList = new ArrayList<SelectOption>();
int month = getDateMonth(expiryDate);
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(true);
} else {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(false);
}
monthList.add(option);
}
return monthList;
}

40. Select Options
public static List<SelectOption> createEndMonthList(Date expiryDate) {
List<SelectOption> monthList = new ArrayList<SelectOption>();
int month = getDateMonth(expiryDate);
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(true);
} else {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(false);
}
monthList.add(option);
}
return monthList;
}

41. Select Options
public static List<SelectOption> createEndMonthList(Date expiryDate) {
List<SelectOption> monthList = new ArrayList<SelectOption>();
int month = getDateMonth(expiryDate);
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(true);
} else {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(false);
}
monthList.add(option);
}
return monthList;
}

42. Select Options
public static List<SelectOption> createEndMonthList(Date expiryDate) {
List<SelectOption> monthList = new ArrayList<SelectOption>();
int month = getDateMonth(expiryDate);
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(true);
} else {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(false);
}
monthList.add(option);
}
return monthList;
}

43. Select Options
public static List<SelectOption> createEndMonthList(Date expiryDate) {
List<SelectOption> monthList = new ArrayList<SelectOption>();
int month = getDateMonth(expiryDate);
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(true);
} else {
option.setLabel(String.valueOf(intLooper));
option.setValue(String.valueOf(intLooper));
option.setSelected(false);
}
monthList.add(option);
}
return monthList;
}

44. Select Options
SelectOptions SelectOptionsSource
create() getFirst()
getLast()
isSelected()
Commonality Variability Resolution
Data Structure Value of State Simple Java Type

45. Select Options
SelectOptions SelectOptionsSource
create() getFirst()
getLast()
isSelected()
Parameter
Object

46. Select Options
SelectOptions SelectOptionsSource
create() getFirst()
getLast()
isSelected()
Commonality Variability Resolution
Encapsulate
Behaviour Collaborator
Collection

47. Select Options
SelectOptions SelectOptionsSource
create() getFirst()
getLast()
isSelected()
Encapsulate
Collection

48. Duplicate Code:
Select Options Extra

49. Select Options Extra
public static List<SelectOption> createProvinceList(String selectedProvince)
{
List<SelectOption> provinceList = new ArrayList<SelectOption>();
List<String> provinces = asList("AB", "BC", "MB", "NB", "NL",
"NT", "NS", "NU", "ON", "PE", "QC", "SK", "YT");
for (int intLooper = 0; intLooper < provinces.size(); intLooper++) {
SelectOption option = new SelectOption();
if (selectedProvince.equals(provinces.get(intLooper))) {
option.setLabel(provinces.get(intLooper));
option.setValue(provinces.get(intLooper));
option.setSelected(true);
} else {
option.setLabel(provinces.get(intLooper));
option.setValue(provinces.get(intLooper));
option.setSelected(false);
}
provinceList.add(option);
}
return provinceList;
}

50. Select Options Extra
public static List<SelectOption> createProvinceList(String selectedProvince)
{
List<SelectOption> provinceList = new ArrayList<SelectOption>();
List<String> provinces = asList("AB", "BC", "MB", "NB", "NL",
"NT", "NS", "NU", "ON", "PE", "QC", "SK", "YT");
for (int intLooper = 0; intLooper < provinces.size(); intLooper++) {
SelectOption option = new SelectOption();
if (selectedProvince.equals(provinces.get(intLooper))) {
option.setLabel(provinces.get(intLooper));
option.setValue(provinces.get(intLooper));
option.setSelected(true);
} else {
option.setLabel(provinces.get(intLooper));
option.setValue(provinces.get(intLooper));
option.setSelected(false);
}
provinceList.add(option);
}
return provinceList;
}

51. Select Options Extra
List<String> provinces = asList("AB", "BC", "MB", "NB", "NL",
"NT", "NS", "NU", "ON", "PE", "QC", "SK", "YT");

52. Select Options Extra
List<String> provinces = asList("AB", "BC", "MB", "NB", "NL",
"NT", "NS", "NU", "ON", "PE", "QC", "SK", "YT");
public enum Province {
AB, BC, MB, NB, NL, NT, NS, NU, ON, PE, QC, SK, YT;
}
Commonality Variability Resolution
A small set of
Data Structure enum
values

53. Select Options Extra
public enum Province {
AB, BC, MB, NB, NL, NT, NS, NU, ON, PE, QC, SK, YT;
}
Single Choice Principle
Whenever a software system must
support a set of alternatives, one
and only one module in the system
should know their exhaustive list.

54. Select Options Extra
public static List<SelectOption> createEndMonthList(Date expiryDate) {
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
}
public static List<SelectOption> createProvinceList(String selectedProvince)
{
for (int intLooper = 0; intLooper < provinces.size(); intLooper++) {
SelectOption option = new SelectOption();
if (selectedProvince.equals(provinces.get(intLooper))) {
option.setLabel(provinces.get(intLooper));
}

55. Select Options Extra
public static List<SelectOption> createEndMonthList(Date expiryDate) {
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
}
public static List<SelectOption> createProvinceList(String selectedProvince)
{
for (int intLooper = 0; intLooper < provinces.size(); intLooper++) {
SelectOption option = new SelectOption();
if (selectedProvince.equals(provinces.get(intLooper))) {
option.setLabel(provinces.get(intLooper));
}

56. Select Options Extra
public static List<SelectOption> createEndMonthList(Date expiryDate) {
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
}
public static List<SelectOption> createProvinceList(String selectedProvince)
{
for (int intLooper = 0; intLooper < provinces.size(); intLooper++) {
SelectOption option = new SelectOption();
if (selectedProvince.equals(provinces.get(intLooper))) {
option.setLabel(provinces.get(intLooper));
}

57. Select Options Extra
public static List<SelectOption> createEndMonthList(Date expiryDate) {
for (int intLooper = 1; intLooper <= 12; intLooper++) {
SelectOption option = new SelectOption();
if (month == intLooper) {
option.setLabel(String.valueOf(intLooper));
}
public static List<SelectOption> createProvinceList(String selectedProvince)
{
for (int intLooper = 0; intLooper < provinces.size(); intLooper++) {
SelectOption option = new SelectOption();
if (selectedProvince.equals(provinces.get(intLooper))) {
option.setLabel(provinces.get(intLooper));
}

58. Select Options Extra
String
Iterable
iterator()
SelectOptions SelectOptionsSource
create() isSelected()
IntegerRangeSource ProvinceSource
iterator() iterator()
isSelected() isSelected()

59. Select Options Extra
String
Iterable
iterator()
SelectOptions SelectOptionsSource
create() isSelected()
IntegerRangeSource ProvinceSource
iterator() iterator()
isSelected() isSelected()

60. Select Options Extra
String
Iterable
iterator()
SelectOptions SelectOptionsSource
create() isSelected()
IntegerRangeSource ProvinceSource
iterator() iterator()
isSelected() isSelected()
Commonality Variability Resolution
Collection Values Iterator

61. Select Options Extra
String
Iterable
iterator()
SelectOptions SelectOptionsSource
create() isSelected()
IntegerRangeSource ProvinceSource
iterator() iterator()
isSelected() isSelected()
Commonality Variability Resolution
Collection Type Generics

62. Select Options Extra
String
Iterable
iterator()
SelectOptions SelectOptionsSource
create() isSelected()
IntegerRangeSource ProvinceSource
iterator() iterator()
isSelected() isSelected()
Commonality Variability Resolution
Inheritance
Behaviour Implementation
(Object-Oriented)

63. Duplicate Code:
Compound Result Handler

64. Compound Result Handler
public Collection<IRegCommand> processCompondResults(Patient sourcePatient, Collection<Result> results) {
Collection<IRegCommand> retVal = new ArrayList<IRegCommand>();
Set<Result> resultsMarkedForRemoval = new HashSet<Result>();
Set<Result> resultsProcessed = new HashSet<Result>();
for (Result primaryResult : results) {
if (isResultProcessed(resultsProcessed, primaryResult)) {
continue;
}
resultsProcessed.add(primaryResult);
Result correspondingResult = getCorrespondingResult(primaryResult, results);
if (correspondingResult != null) {
resultsProcessed.add(correspondingResult);
resultsMarkedForRemoval.add(correspondingResult);
}
if (!sourcePatient.getDataWarehouse().equals(DataWarehouseTag.QHN)) {
// If the response to either question is yes then display positive as the measure value.
if (primaryResult.getDwValue().equalsIgnoreCase("1")) {
primaryResult.setDwValue("POSITIVE");
} else {
// If the response to both questions is no then display negative as the measure value.
if (correspondingResult != null) {
if (correspondingResult.getDwValue().equalsIgnoreCase("2")) {
primaryResult.setDwValue("NEGATIVE");
} else if (correspondingResult.getDwValue().equalsIgnoreCase("1")) {
// It must be yes - thus value is POSITIVE
primaryResult.setDwValue("POSITIVE");
} else {
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"Issue with multiple PHQ results");
continue;
}
} else {
// No corresponding result - where is the 2nd result? -
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"No corresponding value found for a 2 item screener with value of 'no'");
continue;
}
}
} else {
// If the response to either question is yes then display positive as the measure value.
if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
primaryResult.getDwValue().equalsIgnoreCase("4")) {
primaryResult.setDwValue("POSITIVE");
} else {
// If the response to both questions is no then display negative as the measure value.
if (correspondingResult != null) {
if (primaryResult.getDwValue().equalsIgnoreCase("0") ||
primaryResult.getDwValue().equalsIgnoreCase("1") ||
primaryResult.getDwValue().equalsIgnoreCase("2")) {
primaryResult.setDwValue("NEGATIVE");
} else if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
primaryResult.getDwValue().equalsIgnoreCase("4")) {
// It must be yes - thus value is POSITIVE
primaryResult.setDwValue("POSITIVE");
} else {
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"Issue with multiple PHQ results");
continue;
}
} else {
// No corresponding result - where is the 2nd result? -
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"No corresponding value found for a 2 item screener with value of 'no'");
continue;
}
}
}
Map<String, Object> transformedResult = resultTransformer.transformResult(sourcePatient, primaryResult);
if (null != transformedResult) {
retVal.add(new PatientDataUpdateCommand(CommandType.RESULT, sourcePatient, transformedResult));
}
}
return retVal;
}

65. Compound Result Handler
public Collection<IRegCommand> processCompondResults(Patient sourcePatient, Collection<Result> results) {
Collection<IRegCommand> retVal = new ArrayList<IRegCommand>();
Set<Result> resultsMarkedForRemoval = new HashSet<Result>();
Set<Result> resultsProcessed = new HashSet<Result>();
for (Result primaryResult : results) {
if (isResultProcessed(resultsProcessed, primaryResult)) {
continue;
}
resultsProcessed.add(primaryResult);
Result correspondingResult = getCorrespondingResult(primaryResult, results);
if (correspondingResult != null) {
resultsProcessed.add(correspondingResult);
}
resultsMarkedForRemoval.add(correspondingResult);
if (!sourcePatient.getDataWarehouse()
if (!sourcePatient.getDataWarehouse().equals(DataWarehouseTag.QHN)) {
// If the response to either question is yes then display positive as the measure value.
if (primaryResult.getDwValue().equalsIgnoreCase("1")) {
primaryResult.setDwValue("POSITIVE");
.equals(DataWarehouseTag.QHN)) {
} else {
// If the response to both questions is no then display negative as the measure value.
if (correspondingResult != null) {
if (correspondingResult.getDwValue().equalsIgnoreCase("2")) {
primaryResult.setDwValue("NEGATIVE");
} else if (correspondingResult.getDwValue().equalsIgnoreCase("1")) {
// It must be yes - thus value is POSITIVE
primaryResult.setDwValue("POSITIVE");
} else {
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"Issue with multiple PHQ results");
continue;
}
} else {
// No corresponding result - where is the 2nd result? -
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"No corresponding value found for a 2 item screener with value of 'no'");
continue;
}
}
} else {
// If the response to either question is yes then display positive as the measure value.
if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
primaryResult.getDwValue().equalsIgnoreCase("4")) {
primaryResult.setDwValue("POSITIVE");
} else {
// If the response to both questions is no then display negative as the measure value.
if (correspondingResult != null) {
if (primaryResult.getDwValue().equalsIgnoreCase("0") ||
primaryResult.getDwValue().equalsIgnoreCase("1") ||
primaryResult.getDwValue().equalsIgnoreCase("2")) {
primaryResult.setDwValue("NEGATIVE");
} else if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
primaryResult.getDwValue().equalsIgnoreCase("4")) {
// It must be yes - thus value is POSITIVE
primaryResult.setDwValue("POSITIVE");
} else {
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"Issue with multiple PHQ results");
continue;
}
} else {
// No corresponding result - where is the 2nd result? -
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"No corresponding value found for a 2 item screener with value of 'no'");
continue;
}
}
}
Map<String, Object> transformedResult = resultTransformer.transformResult(sourcePatient, primaryResult);
if (null != transformedResult) {
retVal.add(new PatientDataUpdateCommand(CommandType.RESULT, sourcePatient, transformedResult));
}
}
return retVal;
}

66. Compound Result Handler
public Collection<IRegCommand> processCompondResults(Patient sourcePatient, Collection<Result> results) {
Collection<IRegCommand> retVal = new ArrayList<IRegCommand>();
Set<Result> resultsMarkedForRemoval = new HashSet<Result>();
Set<Result> resultsProcessed = new HashSet<Result>();
for (Result primaryResult : results) {
if (isResultProcessed(resultsProcessed, primaryResult)) {
continue;
}
resultsProcessed.add(primaryResult);
Result correspondingResult = getCorrespondingResult(primaryResult, results);
if (correspondingResult != null) {
resultsProcessed.add(correspondingResult);
}
resultsMarkedForRemoval.add(correspondingResult);
if (!sourcePatient.getDataWarehouse().equals(DataWarehouseTag.QHN)) {
if (primaryResult.getDwValue().equalsIgnoreCase("1"))
// If the response to either question is yes then display positive as the measure value.
if (primaryResult.getDwValue().equalsIgnoreCase("1")) {
primaryResult.setDwValue("POSITIVE");
} else {
// If the response to both questions is no then display negative as the measure value.
if (correspondingResult != null) {
if (correspondingResult.getDwValue().equalsIgnoreCase("2")) {
primaryResult.setDwValue("NEGATIVE");
} else if (correspondingResult.getDwValue().equalsIgnoreCase("1")) {
// It must be yes - thus value is POSITIVE
primaryResult.setDwValue("POSITIVE");
} else {
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"Issue with multiple PHQ results");
continue;
}
} else {
// No corresponding result - where is the 2nd result? -
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"No corresponding value found for a 2 item screener with value of 'no'");
continue;
}
} else {
}
if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
// If the response to either question is yes then display positive as the measure value.
if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
primaryResult.getDwValue().equalsIgnoreCase("4")) {
primaryResult.setDwValue("POSITIVE");
primaryResult.getDwValue().equalsIgnoreCase("4"))
} else {
// If the response to both questions is no then display negative as the measure value.
if (correspondingResult != null) {
if (primaryResult.getDwValue().equalsIgnoreCase("0") ||
primaryResult.getDwValue().equalsIgnoreCase("1") ||
primaryResult.getDwValue().equalsIgnoreCase("2")) {
primaryResult.setDwValue("NEGATIVE");
} else if (primaryResult.getDwValue().equalsIgnoreCase("3") ||
primaryResult.getDwValue().equalsIgnoreCase("4")) {
// It must be yes - thus value is POSITIVE
primaryResult.setDwValue("POSITIVE");
} else {
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"Issue with multiple PHQ results");
continue;
}
} else {
// No corresponding result - where is the 2nd result? -
badDataLogger.logBadData(sourcePatient.getExternalId(), Measure.NAME_2ITEMSCREENER,
primaryResult.getDwValue() + " (" + primaryResult.getEventDateTime() + ") ",
"No corresponding value found for a 2 item screener with value of 'no'");
continue;
}
}
}
Map<String, Object> transformedResult = resultTransformer.transformResult(sourcePatient, primaryResult);
if (null != transformedResult) {
retVal.add(new PatientDataUpdateCommand(CommandType.RESULT, sourcePatient, transformedResult));
}
}
return retVal;
}

67. Compound Result Handler
CompoundResultHandler CompoundResultClassifier
isNegative()
isPositive()
AbstractCompoundResultClassifier
toNumber()
QueensCompoundResultClassifier StandardCompoundResultClassifier
isNegative() isNegative()
isPositive() isPositive()

68. Compound Result Handler
CompoundResultHandler CompoundResultClassifier
isNegative()
isPositive()
AbstractCompoundResultClassifier
toNumber()
QueensCompoundResultClassifier StandardCompoundResultClassifier
isNegative() isNegative()
isPositive() isPositive()
Commonality Variability Resolution
Inheritance
Behaviour Implementation
(Object-Oriented)

69. Compound Result Handler
CompoundResultHandler CompoundResultClassifier
isNegative()
isPositive()
AbstractCompoundResultClassifier
toNumber()
QueensCompoundResultClassifier StandardCompoundResultClassifier
isNegative() isNegative()
isPositive() isPositive()
Commonality Variability Resolution
Implementation None Base Class

71. Code Visibility

72. Reading

73. Reading

75. Reading
The Pragmatic Programmer: From Journeyman to Master
Andrew Hunt and Dave Thomas
Extreme Programming Explained: Embrace Change
Kent Beck and Cynthia Andres
Test Driven Development: By Example
Kent Beck
Object-Oriented Software Construction
Bertrand Meyer

76. Reading
Clean Code: A Handbook of Agile Software
Craftsmanship Robert C. Martin
Design Patterns: Elements of Reusable Object-Oriented
Software Erich Gamma, Richard Helm, Ralph Johnson,
and John Vlissides
Multi-Paradigm Design for C++
James O. Coplien
Lean Architecture: for Agile Software Development
James O. Coplien and Gertrud Bjørnvig

77. Photo Credits
http://www.flickr.com/photos/27558040@N00/4151899795/
http://www.flickr.com/photos/popilop/331357312/
http://www.flickr.com/photos/arlette/3260468/
http://www.flickr.com/photos/36829973@N04/3546657245/