GroupBy and SubMap

int groups = 7
//divide list up into groups by % (their remainder)
Map a = (1..50).groupBy({ it % groups }) as TreeMap
assert a.keySet() == (0..<groups) as Set
assert a.keySet() == [0, 1, 2, 3, 4, 5, 6] as Set

//pull out specific keys (plus vals) from a Map
assert a.subMap(1) == [1:[1, 8, 15, 22, 29, 36, 43, 50]]
assert a.subMap([1,2]) == [1:[1, 8, 15, 22, 29, 36, 43, 50], 2:[2, 9, 16, 23, 30, 37, 44]]
assert a.subMap([1,2,99]) == [1:[1, 8, 15, 22, 29, 36, 43, 50], 2:[2, 9, 16, 23, 30, 37, 44], 99:null]
assert a.subMap([1,2,99]).findAll({k,v->!!v}) == [1:[1, 8, 15, 22, 29, 36, 43, 50], 2:[2, 9, 16, 23, 30, 37, 44]]
assert a.subMap((1..3)) == [1:[1, 8, 15, 22, 29, 36, 43, 50], 2:[2, 9, 16, 23, 30, 37, 44], 3:[3, 10, 17, 24, 31, 38, 45]]

Intersect Lists and Maps

List a = [1,2,3]
List b = [2,3,4]
assert [2,3] == a.intersect(b)
assert [1,2,3,4] == (a + b).unique()
assert [1] == a - b
assert [4] == b - a


Map c = [a:1, b:2, c:44]
Map d = [b:2, c:3]
assert [b:2] == c.intersect(d)
assert [a:1, b:2, c:3] == c + d
assert [a:1, b:2, c:44] == d + c
assert [a:1, c:44] == c - d
assert [c:3] == d - c

Random String generator

//see: http://groovyconsole.appspot.com/edit/1032002

String generateToken(Integer size = 16){
    String availableChars = 'ABCDEFGHIJLMNOPQRSTUVXZYabcdefghijlmnopqrstuvxzy0123456789!@#$%*_'
    Random generator = new Random()
    String token = ""
    size.times {
        token += availableChars[generator.nextInt(availableChars.length() - 1)]
    }
    return token
}
 
generateToken()
generateToken(8)

printf with Strings

//all formatting options: http://docs.oracle.com/javase/6/docs/api/java/util/Formatter.html#syntax

//test padding on both sides of "HI"//

(-8..8).each{ i ->
    if (i == 0) i = '' // avoid illegal printf syntax
    
    String f = "**%${i}s**"
    print ((f + ' --> ').padRight(15)) // just for debugging
    printf(f+'\n', "HI")
}


//Tic Tac Toe//

List field = [["","x","o"],["","x",""],["o","",""]]
field.eachWithIndex { line,index ->
    if(index > 0) {
        println "---+" * 2 + "---"
    }
    printf(" %-2s| %-2s| %-2s\n", line)
}

Gradle templates

// Generate a new Groovy Project Qwickly (tm) //
// source: https://github.com/townsfolk/gradle-templates

// in build.gradle file (in the project's root folder):
apply from: 'http://www.tellurianring.com/projects/gradle-plugins/gradle-templates/apply.groovy'

dependencies {
   groovy localGroovy()
}

//then get a list of tasks:
>> gradle tasks

...
Template tasks
--------------
createGroovyClass - Creates a new Groovy class in the current project. **************
createGroovyProject - Creates a new Gradle Groovy project in a new directory named after your project.
createJavaClass - Creates a new Java class in the current project.
createJavaProject - Creates a new Gradle Java project in a new directory named after your project.
exportGroovyTemplates - Exports the default groovy template files into the current directory.
exportJavaTemplates - Exports the default java template files into the current directory.
initGroovyProject - Initializes a new Gradle Groovy project in the current directory. **************
initJavaProject - Initializes a new Gradle Java project in the current directory.
...


>> gradle initGroovyProject
>> gradle createGroovyClass


/**********************************************************/

//Here's a pretty useful project build.gradle:
apply plugin: 'groovy'
apply from: 'http://www.tellurianring.com/projects/gradle-plugins/gradle-templates/apply.groovy'
apply from: 'http://evgenyg.artifactoryonline.com/evgenyg/libs-releases-local/CodeNarc.gradle'

group = 'myapp1'
mainClassName = 'org.MyCompany.Main'

dependencies {
   groovy localGroovy()
}

jar {
    manifest {
        attributes("Main-Class": mainClassName)
    }
}

// uberjar adds in groovy jars to make this easy: "java -jar MyApp.jar"
task uberjar(type: Jar, dependsOn:[':compileJava', ':compileGroovy']) {
    from files(sourceSets.main.output.classesDir)
    from configurations.runtime.asFileTree.files.collect { zipTree(it) }

    manifest {
        attributes 'Main-Class': mainClassName
    }
}

Script template

// this is just intended to give a little more OOP structure to a script.
// put most code inside of run(), plus class variables and methods.

class Script {
    
    private String hello = "Hello"
    
    public Script run(Map options = [:]) {
        println "$hello ${options.name ?: 'World'}${shout(23)}"
        
        
        return this // for method chaining
    }
    
    private String shout(int times = 1) {
        return ('!' * times)
    }
    
}

new Script()
    .run()
    .run([name:'Crazy4Groovy'])

println 'DONE'

Simple Performance Benchmarking

int delayMillis = 100

Long startMillis = Calendar.instance.time.time

Thread.sleep(delayMillis)

Long passedMillis = Calendar.instance.time.time - startMillis

println passedMillis

assert passedMillis >= delayMillis