Operators

Groovy has many operators. Some are reused for different purposes in different contexts. In particular, many are used for operator overloading, allowing the operator to be used on valid objects.

You can read more about operators on the official documentation.

Types of Operators

Arithmetic

The basic math operators are the same as they always are.

Symbol	Name	Operation
a + b	Addition	add a and b
a - b	Subtraction	subtract b from a
a / b	Division	divide a by b
a * b	Multiplication	multiple a by b
a % b	Remainder	get the remainder of dividing a by b
a ** b	Power	a to the power of b

Compound Assignment

You can use several different operators in conjunction with an equal sign to update a variable. This will also implicitly cast the output into the same type as a.

a [op]= b is equivalent to a = a [op] b.

Symbol	Name	Operation
a = b	Assignment	a = b
a += b	Addition	a = a + b
a -= b	Subtraction	a = a - b
a /= b	Division	a = a / b
a *= b	Multiplication	a = a * b
a %= b	Remainder	a = a % b
a **= b	Power	a = a ** b
a ?= b	Elvis	a = a ?: b
a &= b	Bitwise And	a = a & b
a |= b	Bitwise OR	a = a | b
a <<= b	Left Shift	a = a << b
a >>= b	Right Shift	a = a >> b
a >>>= b	Right Shift Unsigned	a = a >>> b

Increment/Decrement

There are two shorthand ways to write a = a + 1 and two to write a = a - 1.

Warning

The two ways differ in what value they return - a++ returns the value of a before being increased, while ++a returns the value of a after being increased. When interacting with these operators, to avoid confusion, you should use them as a standalone statement -

def x = 5
x++
Code.run(x) // do this
Code.run(x++) // don't do this

Symbol	Name	Operation
a++	Postfix Increment	return a; a = a + 1
a--	Postfix Decrement	return a; a = a - 1
++a	Prefix Increment	a = a + 1; return a
--a	Prefix Decrement	a = a - 1; return a

Equality

Compare two values with each other.

Symbol	Name	Operation
a == b	Equals	true if a is the same as b
a != b	Not Equals	true if a is not the same as b
a < b	Less Than	true if a is less than b
a <= b	Less Than or Equal to	true if a is less than or equal to b
a > b	Greater Than	true if a is greater than b
a >= b	Greater Than or Equal to	true if a is greater than or equal to b
a === b	Identical	true if a is identical to b
a !== b	Not Identical	true if a is not identical to b

Logical

Returns a boolean value based on the outcome of the equation. The AND and OR operators will short-circuit, and not run the right hand side if it is not needed. This means you can do things like bool && run(), and run() will only be called if bool is true.

Symbol	Name	Operation
a && b	Logical And	true if both a and b are true
a || b	Logical Or	true if either a or b are true
!a	Logic Not	true if a is false

Bitwise

Bitwise operations are named as such because they directly manipulate bits. Note that bitwise operators do not short-circuit, and will always check both sides of the equation.

Symbol	Name
a & b	Bitwise AND
a | b	Bitwise OR
a ^ b	Bitwise XOR
a ~ b	Bitwise Negation
a << b	Left Shift
a >> b	Right Shift
a >>> b	Right Shift Unsigned

Null Handling

There are some operators to help with handling null, and avoid NullPointerExceptions.

Symbol	Name	Operation
a ? b : c	Ternary	returns b if a is true and c if a is false
a ?: b	Elvis	returns b if a is false, otherwise returns a
a?.b	Safe Navigation	used on an object, will return null if a is null, otherwise will return b
a?[b]	Safe Index	used on an array, will return null if a is null or b is outside of the array

Field Access

Symbol	Name	Operation
a.b	Field access	returns getB if the method exists, otherwise returns the field b
a.@b	Direct field access	returns the field b instead of the method getB()

Method Reference

Symbol	Name	Operation
a.&b	Method pointer	returns a reference to the method b instead of calling it
a::b	Method reference	functionally an alias of a.&b

Regex

Symbol	Name	Operation
~a	Pattern	parses String a into a Regex Pattern
a =~ b	Find	runs ~b, then creates a Matcher against String a
a ==~ b	Match	runs a =~ b, then returns true if there were any matches

Spread

You can manipulate an array of objects

Symbol	Name	Operation
a*.b	Spread	calls b on all items in array a
*a	Arguments	expands the array a into individual elements when calling a method

Range

You can create a range, typically a range of numbers, in a shorthand way. This is typically used as part of a loop or getting a subset of a list.

Symbol	Name	Operation
a..b	Range	Range from a to b, inclusive on both bounds
a<..b	Range	Range from a to b, exclusive on the lower bound and inclusive on the upper bound
a..<b	Range	Range from a to b, inclusive on the lower bound and exclusive on the upper bound
a<..<b	Range	Range from a to b, exclusive on both bounds

Syntax Sugar

Symbol	Name	Operation
<>	Diamond	syntax sugar relating to generic types

Operator Overloading

Groovy has a mechanism where a symbol can be transformed into calling a method on an object. This is a full table of these Operators, and what method they call.

Symbol	Method Called
a + b	a.plus(b)
a - b	a.minus(b)
a * b	a.multiply(b)
a / b	a.div(b)
a % b	a.mod(b)
a ** b	a.power(b)
a | b	a.or(b)
a & b	a.and(b)
a ^ b	a.xor(b)
<=>	a.compareTo(b)
a == b	a.equals(b)
a as b	a.asType(b)
a()	a.call()
a[b]	a.getAt(b)
a[b] = c	a.putAt(b, c)
a in b	b.isCase(a)
a << b	a.leftShift(b)
a >> b	a.rightShift(b)
a >>> b	a.rightShiftUnsigned(b)
a++	a.next()
a--	a.previous()
+a	a.positive()
-a	a.negative()
~a	a.bitwiseNegate()

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481224d-GroovyScript Improvements (#12)