No, a null check is not needed before using instanceof.
x instanceof SomeClass is
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
value of the RelationalExpression is
nulland the reference could be
cast to the ReferenceType
without raising a
Otherwise the result is
So if the operand is null, the result is false.