groovy/groovy-core/xdocs/strings.wiki

1 Strings

Groovy uses both " and ' for strings. Either can be used. Using either
type of string allows you to use strings with quotations easily.

{code:groovysh}
println "he said 'cheese' once"
println 'he said "cheese!" again'
{code}

The groovy parser supports the notation \uab12 (i.e. a leading backslash and precisely four hex digits after the 'u' ).
This notation can be used in strings oranywhere in the program like the Java parser does.

1.1 Multi-line strings

Strings in Groovy can span multiple lines. This makes outputting a large block of text easy.

{code:groovysh}
foo = "hello
 there 
 how are things?"
println(foo)
{code}

1.1 Here-docs

If you have a block of text which you wish to use but don't want to have to encode it all
(e.g. if its a block of HTML or something) then you can use here-docs.

{code:groovysh}
name = "James"
text = <<<FOO
hello there ${name}
how are you today?
FOO

assert text != null
println(text)
{code}


1.1 GStrings

Strings can contain arbitrary expressions inside them as shown above using the 
~~${expression}~~ syntax in a similar way to JSP EL, Velocity and Jexl. 
Any valid Groovy expression can be enclosed in the ${...} including method calls etc

What actually happens is a
{link:GString|http://groovy.codehaus.org/apidocs/groovy/lang/GString.html} object is created
which contains the text and values used inside the String. GString uses lazy evaluation so its not
until the toString() method is invoked that the GString is evaluated. 

This lazy evaluation is useful for things like logging
as it allows the calculation of the string, the calls to toString() on the values and the concatenation of
the different strings to be done laziy if at all.

Another use case for GString is {link:GroovySql|sql.html} where parameters can be passed into SQL statements
using this same mechanism which makes for a neat way to integrate Groovy with other languages like SQL. GroovySql then
converts the expressions to ? and uses a JDBC PreparedStatement and passes the values in, preserving their types.