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: p.ledbrook@cacoethes.co.uk 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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1 of 66

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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