This rule raises an issue when a ternary expression is used to perform a null-safe equality check between two objects.

In Java, this specifically refers to patterns like a != null ? a.equals(b) : b == null that can be replaced with Objects.equals().

Why is this an issue?

Manually checking for null before calling equals() is a common pattern, but it’s verbose and error-prone. Developers must remember to handle all null combinations correctly, which increases the chance of mistakes.

Java provides Objects.equals() as a standard utility method that handles all null cases correctly. Using this method:

• Reduces boilerplate code
• Eliminates the risk of logic errors in null handling
• Makes the intent clearer to other developers
• Follows established Java conventions

The Objects.equals() method is available since Java 7 and is the recommended way to perform null-safe equality comparisons.

What is the potential impact?

Using manual null checks instead of Objects.equals() has several impacts:

• Reduced Readability: The ternary pattern is more complex and requires careful reading to understand the null-handling logic.
• Maintenance Risk: Future developers may misunderstand or incorrectly modify the null-checking logic.
• Inconsistency: Code that mixes manual null checks with Objects.equals() is harder to review and maintain.

While this doesn’t directly cause bugs in correctly written code, it increases cognitive load and the risk of introducing errors during maintenance.

How to fix it

Replace the ternary null-check pattern with Objects.equals(). This handles all null cases correctly in a single method call.

The ternary pattern a != null ? a.equals(b) : b == null returns:

• true when both a and b are null
• true when both are non-null and equal
• false otherwise

This is exactly the behavior of Objects.equals(a, b).

Code examples

Noncompliant code example

if (a != null ? a.equals(b) : b == null) { // Noncompliant
    // ...
}

Compliant solution

if (Objects.equals(a, b)) {
    // ...
}

Resources

Documentation

• Oracle Java Documentation - Objects (Java SE 17 & JDK 17)