Equality

• Referential equality (two references point to the same object);

Structural equality is checked by the == operation (and its negated counterpart !=). By convention, an expression like a == b is translated to:

I.e. if a is not null, it calls the equals(Any?) function, otherwise (i.e. a is null) it checks that b is referentially equal to null.

To provide a custom equals check implementation, override the equals(other: Any?): Boolean function. Functions with the same name and other signatures, like equals(other: Foo), don’t affect equality checks with the operators == and !=.

Structural equality has nothing to do with comparison defined by the Comparable<...> interface, so only a custom equals(Any?) implementation may affect the behavior of the operator.

Otherwise, the structural equality is used, which disagrees with the standard so that is equal to itself, and -0.0 is not equal to 0.0.

See: .