Refactoring to Java 8 (QCon New York)
While we’re drawing ever closer to Java 9, and even hearing about features in Java 10, it’s also true that many of us are still working with an older version. Even if your project has technically adopted Java 8, and even if you’re using it when coding new features, it’s likely the majority of your code base is still not making the most of what’s available in Java 8 - features like Lambda Expressions, the Streams API, and new Date/Time. In this presentation, Trisha: - Highlights some of the benefits of using Java 8 - after all, you’ll probably have to persuade The Management that tampering with existing code is worthwhile - Demonstrates how to identify areas of code that can be updated to use Java 8 features - Shows how to automatically refactor your code to make use of features like lambdas and streams. - Covers some of the pros and cons of using the new features - including suggestions of when refactoring may NOT be the best idea.
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Refactoring to Java 8 (QCon New York)
- 1. Trisha Gee (@trisha_gee) Developer & Technical Advocate, JetBrains Refactoring to Java 8
- 2. Why Java 8?
- 3. It’s Faster •Performance Improvements in Common Data Structures •Fork/Join Speed Improvements •Changes to Support Concurrency •…and more http://bit.ly/refJ8
- 5. Fewer Lines of Code
- 6. New Solutions to Problems
- 8. Safety Check
- 11. Decide on the Goals
- 12. Limit the Scope
- 14. Refactoring!
- 17. Abstract classes
- 18. Advanced Search
- 19. Collections & Streams API
- 20. Automatic Refactoring •For loop to collect •For loop to forEach •…with and without Streams
- 22. Optional
- 24. But what about performance?
- 25. Lambdas
- 26. 0 20 40 60 80 100 120 140 160 180Ops/ms Anonymous Inner Classes vs Lambdas Anonymous Inner Class Lambda
- 27. 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
- 28. 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
- 30. 0 1 2 3 4 5 6 7 8 9 Ops/ms Iterator vs Stream (1000 elements) for loop forEach()
- 31. 0 1000 2000 3000 4000 5000 6000 7000 1 10 100 1000 Ops/ms IterHelper original simplified refactored
- 32. 0 1 2 3 4 5 6 7 8 9 1000 10000 100000 Ops/ms IterHelper original simplified refactored
- 33. BasicDAO – map & collect
- 34. 0 5000 10000 15000 20000 25000 1 10 100 1000 Ops/ms BasicDAO original simplified refactored
- 35. DuplicatedAttributeNames – filter, map & collect
- 39. DatastoreImpl – filter & forEach
- 41. MappingValidator – single stream operation
- 42. 0 100 200 300 400 500 600 700 800 900 EntityWithOneError EntityWith10Errors EntityWith20Errors Ops/ms MappingValidator original refactored
- 43. QueryImpl – multiple operations
- 44. 0 500 1000 1500 2000 2500 3000 3500 Ops/ms QueryImpl original simplified refactored
- 45. Going parallel
- 46. 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
- 48. Optional
- 49. 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
- 50. 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
- 51. Summary
- 52. Sometimes new idioms decrease clutter
- 54. …but sometimes they don’t
- 56. Sometimes the new features improve performance
- 57. 0 20 40 60 80 100 120 140 160 180Ops/ms Anonymous Inner Classes vs Lambdas Anonymous Inner Class Lambda
- 58. …and sometimes they don’t
- 60. Sometimes a new feature makes life easier
- 62. …sometimes not so much
- 64. Some refactoring can safely be done automatically
- 66. …often you need a human brain
- 68. Conclusion
- 69. Should you migrate your code to Java 8?
- 70. It Depends
- 71. Always remember what your goal is And compare results to it
- 72. Understand what may impact performance And if in doubt, measure
- 73. Code may magically improve Or you may expose areas for improvement
- 74. Your tools can help you But you need to apply your brain too