Editing Apache Groovy (section)

===String interpolation===
In Groovy, strings can be interpolated with variables and expressions by using GStrings:<ref>{{cite web |url=http://rajakannappan.blogspot.com.br/2009/12/groovy-strings-different-ways-of.html |title=Groovy Strings - Different ways of creating them |date=26 Dec 2009}}</ref>

<syntaxhighlight lang="groovy">
BigDecimal account = 10.0
def text = "The account shows currently a balance of $account"
assert text == "The account shows currently a balance of 10.0"
</syntaxhighlight>

GStrings containing variables and expressions must be declared using double quotes.

A complex expression must be enclosed in curly brackets. This prevents parts of it from being interpreted as belonging to the surrounding string instead of to the expression:

<syntaxhighlight lang="groovy">
BigDecimal minus = 4.0
text = "The account shows currently a balance of ${account - minus}"
assert text == "The account shows currently a balance of 6.0"

// Without the brackets to isolate the expression, this would result:
text = "The account shows currently a balance of $account - minus"
assert text == "The account shows currently a balance of 10.0 - minus"
</syntaxhighlight>

Expression evaluation can be deferred by employing arrow syntax:

<syntaxhighlight lang="groovy">
BigDecimal tax = 0.15
text = "The account shows currently a balance of ${->account - account*tax}"
tax = 0.10

// The tax value was changed AFTER declaration of the GString. The expression 
// variables are bound only when the expression must actually be evaluated:
assert text == "The account shows currently a balance of 9.000"
</syntaxhighlight>