String Interpolation

Syntax#

$
${}
${->}

Basic

def str = 'nice'
assert "Groovy is $str" == 'Groovy is nice'

Dotted Expression

def arg = [phrase: 'interpolated']
assert "This is $arg.phrase" == 'This is interpolated'

Eager expression

def str = 'old'
def interpolated = "I am the ${str} value"
assert interpolated == 'I am the old value'
str = 'new'
assert interpolated == 'I am the old value'

Lazy expression

We can have lazy interpolation in Strings. This is different than normal interpolation as the GString can potentially have different values, depending on the closure, whenever it is converted into a String.

def str = 'old'
def interpolated = "I am the ${ -> str} value"
assert interpolated == 'I am the old value'
str = 'new'
assert interpolated == 'I am the new value'

Expression

def str = 'dsl'
def interpolated = "Groovy ${str.length() + 1} easy ${str.toUpperCase()}"
assert interpolated == 'Groovy 4 easy DSL'
str = 'Domain specific language'
assert interpolated == 'Groovy 4 easy DSL'