Groovify your Java Code

A guide to Groovy syntax for Java coders

By for Coding Dojo 2014

Interactive slides at:

Hervé Vũ Roussel Agile Vietnam

https://slides.com/hroussel/groovify-your-java-code

Print / bracket, semicol optional

System.out.println("Hello World!");

println "Hello World!"

Return optional

String getCurrentCity() { return "Ho Chi Minh City";}

def getCurrentCity() { "Ho Chi Minh City"}

Try/catch optional

try{ Reader reader = new FileReader("/vietnam-cities.txt")}catch(FileNotFoundException e) { e.printStackTrace()}

def reader = new FileReader("/vietnam-cities.txt")

Duck typing

String s = "Hello"; String c = 'c';Integer i = new Integer(1);BigDecimal d = new BigDecimal(1.2);

def s = "Hello"def c = 'c'def i = 1def d = 1.2

Strong typing

String s = "Hello"; Character = new Character(‘c’);Integer i = new Integer(1);Float d = new Float(1.2);

String s = "Hello"Character c = 'c'Integer i = 1Float f = 1.2

Existential operator (Elvis)

if (city != null) { if (city.getAirport() != null) { city.getAirport().getCode(); }}

city?.getAirport()?.getCode()

Truth

if (1 != 0)if (new City() != null) if ("John".equals(""))if (["HCMC", "Hanoi"].length > 0)

if (1)if (city)if ("John")if (["HCMC", "Hanoi"])

Collections

String [] cities = ["HCMC","Hanoi"];System.out.println(cities[0]);

Map<String,String> airports = new HashMap<String,String>();airports.put("SGN", "Ho Chi Minh City");airports.put("CDG", "Paris");System.out.println(airports.get("SGN"));

def cities = ["HCMC","Hanoi"]println cities[0]

def airports = [SGN:"Ho Chi Minh City", CDG:"Paris"]println airports.SGN

Ranges

List<String> alphabet = new ArrayList<String>();for(int i=0;i<26;i++) { alphabet.add(Character.toChars(i+97));}

def alphabet = "a".."z"

GString

System.out.println("Hello " + user.name);

println "Hello ${user.name}"

Groovy Scripts

public class Script1 { public static void main(String[] args){ String greeting = "Hello " + args[0]; System.out.println(greeting); }}

greeting = "Hello ${args[0]}"println greeting

POGOs

public class City { private String name;

public String getName() { return this.name; } public String setName(String name) { this.name = name; }}

System.out.println(new City("HCMC").getName());

class City { String name}

println new City(name: "HCMC").name

Compare objects

a.equals(b);a.compareTo(b);

a == ba < b

Default parameters

public class Trip { public Trip(String source, String dest, String type) { if (type == null) this.type = "Car"; }}

new Trip("HCMC", "Vung Tau", null);

class Trip { Trip(String source, String dest, String type = "Car") { this.type = type; }}

new Trip("HCMC", "Vung Tau")

Closures

List result = new ArrayList();for(city in city) { if (city.startsWith("H") result.add(city)}

cities.findAll { it.startsWith("H") }

Closures (cont.)

class City { String name}

def cities = [ new City(name: "Mui Ne"), new City(name: "Hanoi")]

cities.collect { it.name + ", VN" } == [ "Mui Ne, VN", "Hanoi, VN" ]cities.any { it.name.indexOf(" ") != -1 } == truecities.every { it.name.indexOf(" ") == -1 } == falsecities.find { it.name.startsWith("H") }.name == "Hanoi"

The End

More on Groovy:

Book: (I didn't write it!)

Slides:Interactive:

PDF:

Thank you!

Free: Groovy User Guide

Groovy Recipes: Greasing the Wheels of Java

Online compiler/runner

http://slides.com/hroussel

https://www.slideshare.net/hroussel

Hervé Vũ Roussel

http://herveroussel.com

Groovify your Java CodeA guide to Groovy syntax for Java coders By Hervé Vũ Roussel for AgileVietnam Coding Dojo 2014 Interactive slides at: https://slides.com/hroussel/groovify-your-java-code

Groovify your Java codeEdit deck title & description

a day ago 0 68Hervé Roussel

http://www.herveroussel.com hvroussel

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