`instanceof` null check needed?

Null Checks Before instanceof: Necessary or Not?

In Java and Spring Boot, null checks before instanceof are generally unnecessary, but context matters. instanceof already handles nulls gracefully; it returns false if the object reference is null.

Why Null Checks are Often Redundant:

The instanceof operator is designed to safely handle null values. Attempting null instanceof SomeClass directly evaluates to false. Adding an explicit null check is therefore redundant and can clutter your code.

Example:

Object obj = someMethod(); // Might return null

if (obj instanceof MyObject) {
    MyObject myObj = (MyObject) obj;
    // ... use myObj ...
}

This code works correctly; no explicit null check is needed. The instanceof check implicitly handles the null case.

When Null Checks Are Necessary:

1. Clarity and Readability: If you have complex logic or want to explicitly handle the null case for better readability, a null check is acceptable.

2. Specific Null Handling: If you need different behavior when the object is null (e.g., logging an error or returning a default value), a null check is required.

Example with Explicit Null Handling:

Object obj = someMethod();

if (obj == null) {
    log.warn("Object is null!");
    return defaultValue; 
} else if (obj instanceof MyObject) {
    MyObject myObj = (MyObject) obj;
    // ... use myObj ...
}

Best Practice: Favor concise code. Omit explicit null checks before instanceof unless strictly required for clarity, specific null handling, or improved readability in complex scenarios. Prioritize clear and maintainable code over unnecessary checks.