在调用 instanceof 之前是否需要进行 null 检查？

Question

Will null instanceof SomeClass return false or throw a NullPointerException?

转载于:https://stackoverflow.com/questions/2950319/is-null-check-needed-before-calling-instanceof

Answer 1

No, a null check is not needed before using instanceof.

The expression x instanceof SomeClass is false if x is null.

From the Java Language Specification, section 15.2.2, "Type comparison operator instanceof":

"At run time, the result of the instanceof operator is true if the value of the RelationalExpression is not null and the reference could be cast to the ReferenceType without raising a ClassCastException. Otherwise the result is false."

So if the operand is null, the result is false.