Working with Strings

Groovy strings come in two flavors: plain strings and GStrings. Plain strings are instances of java.lang.String, and GStrings are instances of groovy.lang.Gstring which allows placeholder expressions to be resolved and evaluated at runtime.

• The single-quoted never pays any attention to placeholders. This is closely equivalent to Java string literals.
• The double-quoted form is the equivalent of the single-quoted form except if the text contains unescaped dollar signs, the dollar sign introduces a placeholder.
• The triple-quoted form allows the literal to span several lines. Multiline string literals may also be GStrings, depending on whether single quotes or double quotes are used.
• The slashy form of string literal is also multiline but allow strings with backslashes to be specified simply without having to escape. This is particularly useful with regular expressions.

GStrings Examples

Abbreviated dollar syntax

def me = 'josdem'
def you = 'Jane'
def line = 'me $me, you $you!'

assert line == 'me josdem you Jane!'

Extended dot syntax

class Person {
  def firstName
  def lastName
}

def person = new Person(firstName:'Jose Luis',lastName:'De la Cruz')
def line = "Person is: $person.firstName $person.lastName"
assert line == 'Person is: Jose Luis De la Cruz'

Full syntax with braces

def date = new Date()
def timeZone = TimeZone.getTimeZone('CST')
def format = 'dd MMM YYYY HH:mm z'
def out = "Date is ${date.format(format, timeZone)}"

assert out == 'Date is 23 Sep 2015 20:41 CDT'

Multiline GStrings

def flower1 = 'Roses'
def flower2 = 'Violets'
def color1 = 'red'
def color2 = 'blue'

def output = """$flower1 are $color1,
$flower2 are $color2,
Sugar is sweet,
And so are you."""

assert output == "Roses are red,
Violets are blue,
Sugar is sweet,
And so are you."

String operations

def greeting = 'Hello Groovy!'

assert greeting.startsWith('Hello')
assert greeting.replaceAll('Hello', 'Hola') == "Hola Groovy!"
assert greeting.getAt(0) == 'H'
assert greeting.indexOf('Groovy') == 6
assert greeting.contains('Groovy')
assert greeting[6..11] == 'Groovy'
assert 'Hi' + greeting - 'Hello' == 'Hi Groovy!'
assert greeting.count('o') == 3
assert 'x' * 3 == 'xxx'

String nickname = 'josdem'
assert nickname.contentEquals('josdem')
assert nickname.contentEquals( new StringBuffer('josdem') )
String string = nickname.replace('dem', 'xyz')
assert string == 'josxyz'

Left operator and StringBuffer

def greeting = 'Hello '
greeting <<= 'Groovy'
assert greeting instanceof java.lang.StringBuffer

greeting << '!'
assert greeting.toString() == 'Hello Groovy!'

greeting[1..4] = 'i'
assert greeting.toString() == 'Hi Groovy!'

Spaceship operator

Groovy adds some nice operators to the language. One of them is the spaceship operator. The operator is another way of referring to the compareTo method of the Comparable interface.

assert -1 == ('a' <=> 'b')
assert 0 == (42 <=> 42)

Compare Persons

class Person implements Comparable {
  String username
  String email

  int compareTo(other) {
      this.username <=> other.username
  }
}

assert 1 == (new Person([username:'josdem', email: 'joseluis.delacruz@gmail.com']) <=> new Person([username:'eric', email:'eric@email.com']))

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