Strings and GString literals

Remarks:

Groovy has two string types the java java.lang.String and groovy.lang.GString, as well as multiple forms of string literals (see syntax and examples).

The main difference between the two types of strings is that GString supports string interpolation.

Single quoted string

def str = 'Single quoted string'
assert str instanceof String

Double quoted string (without interpolation placeholder)

def str = "Double quoted string"
assert str instanceof String

Double quoted string (interpolation)

def param = 'string'
def str = "Double quoted ${param}"
assert str instanceof GString
assert str == 'Double quoted string'

The parameter is by default resolved eagerly, this means this applies:

def param = 'string'
def str = "Double quoted ${param}"
param = 'another string'
assert str == 'Double quoted string'

In order to load the parameter lazily every time the string is used, this can be done:

def param = 'string'
def str = "Double quoted ${ -> param}"
assert str == 'Double quoted string'
param = 'lazy load'
assert str == 'Double quoted lazy load'

Multiline string

def str = '''multiline 
string'''
assert str instanceof String

Multiline string (extra trailing newline)

def str = '''
multiline 
string'''
assert str.readLines().size() == 3

Multiline string (without extra trailing newline)

def str = '''\
multiline 
string'''
assert str.readLines().size() == 2

Triple double quoted string

def param = 'string'
def str = """
multiline
$param
"""
assert str instanceof GString
assert str.readLines().size() == 3
assert str == '''
multiline
string
'''

Slashy string (no interpolation placeholder)

def str = /
multiline string
no need to escape slash
\n
/
assert str instanceof String
assert str.readLines().size() == 4
assert str.contains('\\n')

Slashy string (interpolation)

def param = 'string'
def str = /
multiline $param
no need to escape slash
\n
/
assert str instanceof GString
assert str.readLines().size() == 4
assert str.contains('\\n')
assert str.contains('string')

Dollar slash string

def param = 'string'
def str = $/
multiline $param
no need to escape slash
\n
$
$$
/$
assert str instanceof GString
assert str.readLines().size() == 6
assert str.contains('\\n')
assert str.contains('$')

Syntax:

'Single quoted string'
"Double quoted string"
'''Multiline string'''
"""Triple double quoted string"""
/Slashy string/
$/Dollar slash string/$

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Topic Id: 3409

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