Learning Groovy

4. GDK

Collections

sort: Sorts the collection (if it is sortable).
findAll: Finds all elements that match a closure.
collect: An iterator that builds a new collection.
inject: Loops through the values and returns a single value.
each: Iterates through the values using the given closure.
eachWithIndex: Iterates through with two parameters: a value and an index.
find: Finds the first element that matches a closure.
findIndexOf: Finds the first element that matches a closure and returns its index.
any: True if any element returns true for the closure.
every: True if all elements return true for the closure.
reverse: Reverses the ordering of elements in a list.
first: Gets the first element of a list.
last: Returns the last element of a list.
tail: Returns all elements except the first element of a list.

Spread

dragons*.name.each { println it }

GPath

def listOfMaps = [['a': 11, 'b': 12], ['a': 21, 'b': 22]]
assert listOfMaps.a == [11, 21] //GPath notation
assert listOfMaps*.a == [11, 21] //spread dot notation

listOfMaps = [['a': 11, 'b': 12], ['a': 21, 'b': 22], null ]
assert listOfMaps*.a == [11, 21, null ] // caters for null values
assert listOfMaps*.a == listOfMaps.collect { it?.a } //equivalent notation
// But this will only collect non-null values
assert listOfMaps.a == [11,21]

IO

Files

// For binary files, you can also use the `bytes` property:
byte[] data = new File('data').bytes
new File('out').bytes = data

// If you want to use an InputStream or reader
// or the corresponding OutputStream or
// writer for output, you have the following methods:
new File('dragons.txt').withInputStream { in -> }
new File('dragons.txt').withReader {r -> }
new File('dragons.txt').withOutputStream {out ->}
new File('dragons.txt').withWriter {w -> }

// You can use the `eachLine` method to read each line of a file:
new File('dragons.txt').eachLine { line->
    println "$line"
}

// OR
new File('dragons.txt').eachLine { line, num ->
    println "Line $num: $line"
}

URLs

println "http://google.com".toURL().text