Strings and GStrings

Integration work is full of text: JSON payloads, file names, log messages, SQL. Groovy makes building and picking apart text much easier than Java.

Single quotes vs double quotes

def customer = 'Acme'
println "Customer $customer owes ${amount * 1.2}"    // GString: interpolated
println 'Customer $customer'                          // plain String: printed as-is

Double quotes create a GString: $variable or ${expression} is replaced by its value. Use single quotes when you don’t need interpolation (and when the text contains $).

Watch out: A GString isn’t a java.lang.String. Where a Java API needs a real String — map keys, Properties.setProperty, some Boomi calls — call .toString() on it.

Multi-line strings

def json = """{
  "customer": "$customer",
  "amount": $amount
}"""

Triple single quotes '''…''' give multi-line text without interpolation. stripIndent() removes the common leading spaces so code can stay nicely indented.

Slashy strings and regular expressions

Backslashes don’t need escaping inside /…/, which makes regular expressions readable:

def skuPattern = /[A-Z]{2}-\d{3}/
'AX-200' ==~ skuPattern                                       // true: the WHOLE string matches
('Order AX-200 and BX-310' =~ skuPattern).findAll()           // [AX-200, BX-310]: find inside

• ==~ — does the whole string match? (boolean)
• =~ — a matcher for finding occurrences.

Methods Groovy adds to String

'po-4471'.toUpperCase().padLeft(10, '*')   // ***PO-4471
'a,b,,c'.tokenize(',')                     // [a, b, c]  (split() would keep the empty one)
'hello world'.capitalize()                  // Hello world
'42'.isInteger() ? '42'.toInteger() : 0     // 42
'Boomi'[0..2]                               // Boo — ranges as indexes
'Boomi'[-1]                                 // i   — negative index counts from the end
'ab' * 3                                    // ababab
'Acme Ltd' - ' Ltd'                         // Acme — remove the first occurrence

The full example

// strings.groovy — single quotes, GStrings, multi-line strings and string methods.
def customer = 'Acme'                       // plain String
def amount = 204.5

// GString: double quotes with ${...} or $variable
println "Customer $customer owes ${amount * 1.2}"

// Single quotes never interpolate
println 'Customer $customer owes ${amount}'

// Triple quotes: multi-line
def json = """{
  "customer": "$customer",
  "amount": $amount
}"""
println json

// Slashy strings: great for regular expressions (no double escaping)
def skuPattern = /[A-Z]{2}-\d{3}/
println 'AX-200' ==~ skuPattern             // true: whole-string match
def found = ('Order AX-200 and BX-310' =~ skuPattern).findAll()
println found                                // [AX-200, BX-310]

// Handy String methods added by Groovy
println 'po-4471'.toUpperCase().padLeft(10, '*')   // ***PO-4471
println 'a,b,,c'.tokenize(',')                     // [a, b, c]  (split keeps empties)
println 'hello world'.capitalize()                  // Hello world
println '42'.isInteger() ? '42'.toInteger() + 1 : 'not a number'   // 43
println 'Boomi'[0..2]                               // Boo
println 'Boomi'[-1]                                 // i
println 'ab' * 3                                    // ababab
println 'Acme Ltd' - ' Ltd'                         // Acme

// Multi-line text with stripIndent
def message = '''\
    Dear customer,
      your order has shipped.
    '''.stripIndent()
print message

Try it yourself

Given def line = 'PO-4471|Acme Ltd|24|8.50', print Acme Ltd ordered 24 × PO-4471 = 204.00 using tokenize and a GString.

def line = 'PO-4471|Acme Ltd|24|8.50'
def (id, customer, qty, price) = line.tokenize('|')
println "$customer ordered $qty × $id = ${qty.toInteger() * price.toBigDecimal()}"

Key takeaways

• Double quotes interpolate ($x, ${expr}); single quotes don’t.
• Triple quotes for multi-line text; slashy strings for regex.
• ==~ matches a whole string, =~ finds within it.
• Groovy adds many helpers: tokenize, padLeft, ranges as indexes, * and -.