Trisha Gee (@trisha_gee)

Developer & Technical Advocate, JetBrains

Refactoring to Java 8

Why Java 8?

It’s Faster

•Performance Improvements in Common Data Structures

•Fork/Join Speed Improvements

•Changes to Support Concurrency

•…and more

http://bit.ly/refJ8

Easy to Parallelize

Fewer Lines of Code

New Solutions to Problems

Minimizes Errors

Safety Check

Test Coverage

Performance Tests

Decide on the Goals

Limit the Scope

Morphia

https://github.com/mongodb/morphia

Refactoring!

Lambda Expressions

Automatic Refactoring

•Predicate

•Comparator

•Runnable

•etc…

Abstract classes

Advanced Search

Collections & Streams API

Automatic Refactoring

•For loop to collect

•For loop to forEach

•…with and without Streams

Manual Refactoring

Optional

But what about performance?

Lambdas

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180O

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Anonymous Inner Classes vs Lambdas

Anonymous Inner Class Lambda

http://www.oracle.com/technetwork/java/jvmls2013kuksen-2014088.pdf

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nse

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Performance of Capture

anonymous(static) anonymous(non-static) lambda

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Constant message Variable message

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sLogging Performance

Direct call Lambda

Streams vs Iteration

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s/m

sIterator vs Stream (1000 elements)

for loop forEach()

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s/m

sIterHelper

original simplified refactored

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sIterHelper

original simplified refactored

BasicDAO – map & collect

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BasicDAO

original simplified refactored

DuplicatedAttributeNames – filter, map & collect

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s/m

sDuplicatedAttributeNames

original refactored

EntityScanner– forEach

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Op

s/m

sEntityScanner

original refactored

DatastoreImpl – filter & forEach

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s/m

sDatastoreImpl

original refactored

MappingValidator – single stream operation

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EntityWithOneError EntityWith10Errors EntityWith20Errors

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s/m

sMappingValidator

original refactored

QueryImpl – multiple operations

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s/m

sQueryImpl

original simplified refactored

Going parallel

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Serial Parallel

Tim

e Ta

ken

(se

con

ds)

map()

MacBook Surface

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Serial Parallel

Tim

e Ta

ken

(m

illis

)findAny()

MacBook Surface

Optional

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Value not null Value null

Op

s/m

sCompare Constant Field Value with Null

Null check Optional

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Value not null Value null

Op

s/m

sCompare Variable Field Value with Null

Null check Optional

Summary

Sometimes new idioms decrease clutter

…but sometimes they don’t

Sometimes the new features improve performance

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60

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100

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180O

ps/

ms

Anonymous Inner Classes vs Lambdas

Anonymous Inner Class Lambda

…and sometimes they don’t

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Op

s/m

sDuplicatedAttributeNames

original refactored

Sometimes a new feature makes life easier

…sometimes not so much

Some refactoring can safely be done automatically

…often you need a human brain

Conclusion

Should you migrate your code to Java 8?

It Depends

Always remember what your goal is

And compare results to it

Understand what may impact performance

And if in doubt, measure

Code may magically improve

Or you may expose areas for improvement

Your tools can help you

But you need to apply your brain too

http://bit.ly/refJ8

@trisha_gee