Video and slides synchronized, mp3 and slide download available at URL http://bit.ly/2c8so2f. Trisha Gee highlights the performance benefits of using Java 8. Gee demonstrates how to identify areas of code that can be updated to use Java 8 features, how to pick which changes will give the most benefit and how to automatically refactor a code to make use of features like lambdas and streams. She covers some of the pros and cons of using the new features. Filmed at qconnewyork.com. Trisha Gee has developed Java applications for a range of industries, including finance, manufacturing, technology, open source and non-profit, for companies of all sizes. She has expertise in Java high performance systems, and is passionate about enabling developer productivity. Trisha is a leader of the Sevilla Java User Group, a key member of the London Java Community and a Java Champion.

1. Trisha Gee (@trisha_gee)
Developer & Technical Advocate, JetBrains
Refactoring to
Java 8

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Watch the video with slide
synchronization on InfoQ.com!
https://www.infoq.com/presentations/
java8-lambda-streams

3. Presented at QCon New York
www.qconnewyork.com
Purpose of QCon
- to empower software development by facilitating the spread of
knowledge and innovation
Strategy
- practitioner-driven conference designed for YOU: influencers of
change and innovation in your teams
- speakers and topics driving the evolution and innovation
- connecting and catalyzing the influencers and innovators
Highlights
- attended by more than 12,000 delegates since 2007
- held in 9 cities worldwide

4. Why Java 8?

5. It’s Faster
•Performance Improvements in Common Data
Structures
•Fork/Join Speed Improvements
•Changes to Support Concurrency
•…and more
http://bit.ly/refJ8

6. Easy to Parallelize

7. Fewer Lines of Code

8. New Solutions to Problems

9. Minimizes Errors

10. Safety Check

11. Test Coverage

12. Performance Tests

13. Decide on the Goals

14. Limit the Scope

15. Morphia
https://github.com/mongodb/morphia

16. Refactoring!

17. Lambda Expressions

18. Automatic Refactoring
•Predicate
•Comparator
•Runnable
•etc…

19. Abstract classes

20. Advanced Search

21. Collections & Streams API

22. Automatic Refactoring
•For loop to collect
•For loop to forEach
•…with and without Streams

23. Manual Refactoring

24. Optional

26. But what about performance?

27. Lambdas

28. 0
20
40
60
80
100
120
140
160
180Ops/ms
Anonymous Inner Classes vs Lambdas
Anonymous Inner Class Lambda



29. http://www.oracle.com/technetwork/java/jvmls2013kuksen-2014088.pdf
0
2
4
6
8
10
12
14
16
18
20
single thread max threads
nsec/op
Performance of Capture
anonymous(static) anonymous(non-static) lambda 


30. 

0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
400,000
450,000
500,000
Constant message Variable message
Ops/ms Logging Performance
Direct call Lambda

31. Streams vs Iteration

32. 0
1
2
3
4
5
6
7
8
9
Ops/ms Iterator vs Stream (1000 elements)
for loop forEach()



33. 0
1000
2000
3000
4000
5000
6000
7000
1 10 100 1000
Ops/ms
IterHelper
original simplified refactored



34. 0
1
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5
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9
1000 10000 100000
Ops/ms IterHelper
original simplified refactored



35. BasicDAO – map & collect

36. 0
5000
10000
15000
20000
25000
1 10 100 1000
Ops/ms
BasicDAO
original simplified refactored



37. DuplicatedAttributeNames – filter, map & collect

38. 0
200
400
600
800
1000
1200
Ops/ms
DuplicatedAttributeNames
original refactored



39. EntityScanner– forEach

40. 

0
0.01
0.02
0.03
0.04
0.05
0.06
Ops/ms
EntityScanner
original refactored

41. DatastoreImpl – filter & forEach

42. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Ops/ms
DatastoreImpl
original refactored



43. MappingValidator – single stream operation

44. 

0
100
200
300
400
500
600
700
800
900
EntityWithOneError EntityWith10Errors EntityWith20Errors
Ops/ms
MappingValidator
original refactored

45. QueryImpl – multiple operations

46. 0
500
1000
1500
2000
2500
3000
3500
Ops/ms QueryImpl
original simplified refactored



47. Going parallel

48. 0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
Serial Parallel
TimeTaken(seconds) map()
MacBook Surface



49. 0
20
40
60
80
100
120
140
160
Serial Parallel
TimeTaken(millis) findAny()
MacBook Surface



50. Optional

51. 0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
Value not null Value null
Ops/ms
Compare Constant Field Value with Null
Null check Optional



52. 0
50,000
100,000
150,000
200,000
250,000
300,000
Value not null Value null
Ops/ms
Compare Variable Field Value with Null
Null check Optional



53. Summary

54. Sometimes new idioms decrease clutter

56. …but sometimes they don’t

58. Sometimes the new features improve
performance

59. 0
20
40
60
80
100
120
140
160
180Ops/ms
Anonymous Inner Classes vs Lambdas
Anonymous Inner Class Lambda



60. …and sometimes they don’t

61. 0
200
400
600
800
1000
1200
Ops/ms
DuplicatedAttributeNames
original refactored



62. Sometimes a new feature makes life easier

64. …sometimes not so much

66. Some refactoring can safely be done
automatically

68. …often you need a human brain

70. Conclusion

71. Should you migrate your code to Java 8?

72. It Depends

73. Always remember what your goal is
And compare results to it

74. Understand what may impact performance
And if in doubt, measure

75. Code may magically improve
Or you may expose areas for improvement

76. Your tools can help you
But you need to apply your brain too

77. http://bit.ly/refJ8
@trisha_gee

78. Watch the video with slide synchronization on
InfoQ.com!
https://www.infoq.com/presentations/java8-
lambda-streams