5 min read
Data Types
Prerequisites: Variables and def
Every value in Groovy is an object with a class — even numbers. Groovy uses Java's types and adds a few conveniences on top.
println 42.getClass().name
println 3.14.getClass().name
println 'text'.getClass().name
println "sum: ${1 + 1}".getClass().name
println true.getClass().name
println ([1, 2].getClass().name)
println ([a: 1].getClass().name)
println ((1..3).getClass().name)
println ({ it }.getClass().superclass.name)
java.lang.Integer
java.math.BigDecimal
java.lang.String
org.codehaus.groovy.runtime.GStringImpl
java.lang.Boolean
java.util.ArrayList
java.util.LinkedHashMap
groovy.lang.IntRange
groovy.lang.Closure
| Literal | Type |
|---|---|
42 |
Integer (grows to Long or BigInteger if too big) |
3.14 |
BigDecimal — exact decimal, not double |
'text' |
String |
"sum: ${...}" |
GString (a string with placeholders) |
true / false |
Boolean |
[1, 2] |
ArrayList |
[a: 1] |
LinkedHashMap (keeps insertion order) |
1..3 |
IntRange |
{ it } |
Closure |
null |
no object at all |
Checking types
def value = 42
println value instanceof Integer
println value instanceof Number
println value in Number // "in" also checks class membership
def nothing = null
println nothing == null
println nothing?.getClass() // ?. avoids calling a method on null
true
true
true
true
null
Converting between types
println '42' as int
println '42'.toInteger() + 1
println '3.5'.toBigDecimal() * 2
println 42.toString() + '!'
println 65 as char
println 'yes'.isNumber()
42
43
7.0
42!
A
false
as converts ("coerces") a value to a type; toInteger(),
toBigDecimal(), and friends are Groovy's additions to String.
isNumber() checks first, which is useful for user input.
Primitives
You can declare Java primitives (int, double, boolean, ...), and
Groovy boxes them into objects when needed. In dynamic code the
difference rarely matters; with static compilation, primitives are faster.