Convert String to an int

How to convert a String to an int ?

String str = "1234";

Integer x = Integer.valueOf(str);
// or
int y = Integer.parseInt(str);

Groovy : Use Collect with Initial Collection Value

The collect() method in Groovy can be used to iterate over collections and transform each element of the collection. The transformation is defined in as a closure and is passed to the collect() method. But we can also add an initial collection to which the transformed elements are added.


// Collect without
// initial collection.
assert [0,2,4,6] == (0..3).collect { it * 2 }
assert ['Groovy', 'Grails'] == [lang: 'Groovy', framework: 'Grails'].collect { it.value }

// Collect with initial collection argument.
assert [0, 1, 2, 3] == [2, 3].collect([0, 1]) { it }
assert [0, 3, 6, 9] == [2, 3].collect([0, 3], { it * 3})
assert ['Gradle', 'groovy', 'grails'] == ['Groovy', 'Grails'].collect(['Gradle']) { it.toLowerCase() }
assert ['m','r','h','a','k','i'] == [4, -3, 7, 5].collect(['m', 'r']) { (it + 100) as char }

Groovy : Regular Expressions example

In Groovy we use the =~ operator (find operator) to create a new matcher object. If the matcher has any match results we can access the results by invoking methods on the matcher object. But Groovy wouldn't by groovy if we could access the results easier. Groovy enhances the Matcher class so the data is available with an array-like syntax. If we use groups in the matcher the result can be accessed with a multidimensional array. Although the result of the =~ operator is a matcher object in a conditional statement the result will be converted to a Boolean values.

We can use a second operator, ==~ (match operator), to do exact matches. With this operator the matches() method is invoked on the matcher object. The result is a Boolean value.


def finder = ('groovy' =~ /gr.*/)
assert finder instanceof java.util.regex.Matcher

def matcher = ('groovy' ==~ /gr.*/)
assert matcher instanceof Boolean

assert 'Groovy rocks!' =~ /Groovy/  // =~ in conditional context returns boolean.
assert !('Groovy rocks!' ==~ /Groovy/)  // ==~ looks for an exact match.
assert 'Groovy rocks!' ==~ /Groovy.*/

def cool = /gr\w{4}/  // Start with gr followed by 4 characters.
def findCool = ('groovy, java and grails rock!' =~ /$cool/)
assert 2 == findCool.count
assert 2 == findCool.size()  // Groovy adds size() method.
assert 'groovy' == findCool[0]  // Array-like access to match results.
assert 'grails' == findCool.getAt(1)

// With grouping we get a multidimensional array.
def group = ('groovy and grails, ruby and rails' =~ /(\w+) and (\w+)/)
assert group.hasGroup()
assert 2 == group.size()
assert ['groovy and grails', 'groovy', 'grails'] == group[0]
assert 'rails' == group[1][2]

// Use matcher methods.
assert 'Hi world' == ('Hello world' =~ /Hello/).replaceFirst('Hi')

// Groovy matcher syntax can be used in other methods.
assert ['abc'] == ['def', 'abc', '123'].findAll { it =~ /abc/ }
assert [false, false, true] == ['def', 'abc', '123'].collect { it ==~ /\d{3}/ }

Intellij idea: search anything with file extension

1. Press Ctrl+shift+f button

2. Check mark "file mask" checkbox

3. Enter extension "*. example" in this format