Will null instanceof SomeClass
return false
or throw a NullPointerException
?
No, a null check is not needed before using instanceof.
The expression x instanceof SomeClass
is false
if x
is null
.
The Java 11 Language Specification expresses this concisely in section 15.20.2, “Type comparison operator instanceof”. (Java 17 expresses this less concisely, after the introduction of instanceof patternmatching.)
“At run time, the result of the
instanceof
operator istrue
if the
value of the RelationalExpression is
notnull
and the reference could be
cast to the ReferenceType
without raising aClassCastException
.
Otherwise the result isfalse
.”
So if the operand is null, the result is false.