Download - How to get Groovy with Java 8
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How to get Groovy with Java 8Peter Ledbrook
w: http://www.cacoethes.co.uk/ e: [email protected] t: @pledbrook
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Groovy devs tend to look down on Java
Severus Snape - copyright Warner Bros. under fair use
Show me filtering
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List<String> filterList(List<String items) { List<String> result = new ArrayList<>(items.size()); for (String item : items) { if (item.startsWith("idx_")) { result.add(item); } } return result; }
items.findAll { it.startsWith("idx_") }
compared to
But it’s just syntax sugar!
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Readable vs comprehensible
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Mrs Dalloway (Virginia Woolf)
vs
Macbeth (Shakespeare)
The Firm (John Grisham)
vs
Any aid to comprehension is good
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Aside
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Code as if you’re the poor sod who has to maintain it later
But now…
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Lambda functions + Streams API
Java is superior !!!! Mwuhaahaahaa
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has a stupid name is slow is a “poor language” has no type safety
Groovy:
Java vs Groovy
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Challenge!
Groovy over Java 8
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Type inferenceUseful literals
Scripts
Regular expressions
Don’t forget
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Groovy JDKOperator overloading
JSON/XML generation & parsing
Property syntax
Can Java do Gradle builds?
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Or a Spock test?
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So Java still sucks, right?
Yes, Groovy is more expressive
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But Project Coin + Java 8 are a big improvement
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Java advantages
• A pretty stable language and runtime
• Commitment to backwards/forwards compatibility
• Consider erasure and target compatibility
• Less affected by JVM bugs than other languages
• Other JVM languages have to integrate with it
• Few binary incompatibilities
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JVM bugs
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In @CompileStatic we trust?
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Risk assessment is crucial
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Example approach: Ratpack
• Core library in Java
• Groovy API
• Fully type safe if desired
• Apps can be written in any JVM language
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Demo
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Don’t view Groovy & Java as competing languages
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Let’s be friends!
Black and Orange Kittens Hugging By Alarob (Creative Commons)
So what does Java 8 do for Groovy?
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Closures in place of lambdas
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With type safety
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This call satisfies type checker!
Groovy coerces closures to single-method interfaces
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Lambda functions based on invoke dynamic & method handles
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Performance (Java 8, no indy)
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Fibonacci(1000) Ops/s Error
Groovy 14182.438 324.031
@CompileStatic 19773.641 373.737
Java 19944.132 381.222
Performance (Java 8, indy)
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Fibonacci(1000) Ops/s Error
Groovy 18917.895 272.131
@CompileStatic 19471.877 376.576
Java 19883.443 312.094
Performance (Java 7, indy)
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Fibonacci(1000) Ops/s Error
Groovy 19031.570 251.189
@CompileStatic 21464.016 246.329
Java 20181.067 82.275
APIs
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Dates & Times
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Groovy TimeCategory
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Groovy JDK enhancements incoming?
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Enhanced Java 7 File NIO
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Streams API
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Streams API
• Richer than Groovy JDK
• Lazy collections
• Simple parallelisation
• Typed functions
• map(), mapToInt(), mapToObj(), etc.
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What about default methods?
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Default method in interface
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Better option: Groovy traits
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Example
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Demo
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Groovy traits
• Supports state (properties & fields)
• Multiple inheritance
• default conflict resolution
• user-specified conflict resolution
• Ideal for object composition
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And remember, all the Groovy stuff works on JDK 6+
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Summary
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Thank you!
Q & A
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