In Kotlin, ==
means structural equality and !=
structural inequality and both map to the left-side term’s
equals()
function. It is, therefore, redundant to call equals()
as a function. Also, ==
and !=
are
more general than equals()
and !equals()
because it allows either of both operands to be null
.
Developers using equals()
instead of ==
or !=
is often the result of adapting styles from other languages
like Java, where ==
means reference equality and !=
means reference inequality.
What is the potential impact?
Wrong logic
==
and !=
allow either of both operands to be null
, while equals()
doesn’t.
Readability and Understanding
The ==
and !=
operators are a more concise and elegant way to test structural equality than calling a function.