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March 8, 2020

Groovy Goodness: Check Object Instances Are The Same With === Operator

Groovy has used the == operator to check if objects are equal for a long time. To test if object instances are the same we must use the is method. Groovy 3 adds a new operator for the is method and that is the === operator. And to negate the result of the is method we can use the !== operator.

In the following example we use the === and !== operator to check if objects refer to the same instance or not:

def answer = new Integer(42)
def anotherAnswer = new Integer(42)
def meaningOfLife = answer

// Equals is true for answer and anotherAnswer
assert answer == anotherAnswer

// But they don't refer to the same instance.
assert answer !== anotherAnswer

// The variables meaningOfLife and answer
// do refer to the same object instance.
assert answer === meaningOfLife

Written with Groovy 3.0.2.