<!--
title: Validate nulls properly
domain: app-frameworks
topic: Null Handling
language: Java
source: spring-projects/spring-boot
updated: 2024-12-04
url: https://awesomereviewers.com/reviewers/spring-boot-validate-nulls-properly/
-->

Always use appropriate null validation mechanisms to prevent NullPointerExceptions and ensure code robustness.

For string parameters:
- Use `Assert.hasText(profile, "Profile must have text")` instead of `Assert.notNull()` when you need to validate both null and empty strings
- This handles both null checks and empty string validation in one call

For equals methods:
- Always check for null before comparing class types:
```java
@Override
public boolean equals(Object obj) {
    if (this == obj) {
        return true;
    }
    if (obj == null || getClass() != obj.getClass()) {
        return false;
    }
    // Continue with comparison
}
```

For collections and arrays:
- Always validate that collection parameters are not null before processing them
- For optional collections, consider:
```java
if (resolvers != null) {
    // process resolvers
}
```
- Or enforce non-null values through constructor validation

Using these patterns consistently will reduce null-related bugs and improve code quality across the codebase.