02-groovy-for-java-devs.groovy

gistfile1.groovy

/* 
        ________________     ______                           
       / ____/_  __/ __ \   / ____/________  ____ _   ____  __
      / /_    / / / / / /  / / __/ ___/ __ \/ __ \ | / / / / /
     / __/   / / / /_/ /  / /_/ / /  / /_/ / /_/ / |/ / /_/ / 
    /_/     /_/ /_____/   \____/_/   \____/\____/|___/\__, /  
                                                     /____/  
    12/03/2015
    
    @ftmamud
    https://friendstechday.wordpress.com/
    Differences from Java
*/



// Compare Java Bean & Groovy Bean
// Public by default
// Getters and Setters

def p = "FTD"
def showEvent(what) {
    println what
}

showEvent(p)

// default

class Pessoa {
    Integer id
    String name
    
    def getId() {
        ""
    }
}

def p = new Pessoa(id:1, name:"Groovy")
println p.id
p.name = "Java"
println "$p.id $p.name"



// Return keyword optional

/* Groovy Default imports \o/

    java.io.*
    java.lang.*
    java.math.BigDecimal
    java.math.BigInteger
    java.net.*
    java.util.*
    groovy.lang.*
    groovy.util.*
*/

new File(".").absolutePath

/* Groovy Script Binding

    String eventName = "ftd"
    void showEventName(){
      assert eventName == "ftd" // Not allowed !
    }
    showEventName()
    
*/


// def or Object (Multi-methods: override methods problems)

class Printador {
    void print(String texto) {
        println "String $texto"
    }
    
    void print(Object texto) {
        println "Object $texto"
    }
}

Object texto = "Vamos embora?"
new Printador().print(texto)

def show(obj) {
    println obj
}
show(o)

// GDK - http://groovy-lang.org/gdk.html

String.metaClass.ftd = {
    "Groovy Rocks!"
}

"Qual linguagem domina?".ftd()


[1,2,3,4,5].sum()

// Class first citizen (properties)

println String.properties

// Array initializers

//Java way: int[] arr = new int[] { 1,2,3 };

// Groovy way
int[] arr = [1,2,3]
arr.class

// Protected , @groovy.transform.PackageScope
import groovy.transform.PackageScope
class Person {
    @PackageScope String name
}


// Automatic Resource Management : Try with resources

new File('names.txt').withReader('UTF-8') { reader ->
   reader.eachLine {
       println it
   }
}

// Java 8 == Closures  [1, 2, 3].stream()

[1,2,3].stream().map { it ** 2 }.forEach { println it }

// static with 'this'



// checked and unchecked exceptions

new File('names.txt').text

// newline at the wrong place into the code
myVariable = "FTD Groovy: "
    + 42             // this line has no effect*/