Do Not Throw NullPointerException

ID

java.no_throw_npe

Severity

high

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Reliability

Language

Java

Tags

CWE:248, reliability

Description

Reports throw new NullPointerException(…​) statements.

Rationale

Explicitly throwing NullPointerException is almost always a code smell. In stack traces it is indistinguishable from a genuine null-dereference bug, making diagnosis harder. Callers who see NullPointerException cannot tell whether the failure is an argument-validation guard or an accidental null access.

// Bad -- looks like a real NPE bug in stack traces
public void process(String input) {
    if (input == null) {
        throw new NullPointerException("input is null");
    }
}

Remediation

Use IllegalArgumentException for argument validation or Objects.requireNonNull() for null-guard preconditions:

// Good -- clear semantics
public void process(String input) {
    if (input == null) {
        throw new IllegalArgumentException("input must not be null");
    }
}

// Good -- concise precondition
public void process(String input) {
    Objects.requireNonNull(input, "input must not be null");
}

References