Inefficient Empty String Test

java.inefficient_empty_string_test

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Efficiency

Language

Java

Description

Reports two idioms commonly used to test whether a String is empty and that are both clearer and marginally faster when replaced by String.isEmpty():

s.equals("")
s.length() == 0 (and its symmetric form 0 == s.length())

Rationale

s.equals("") goes through the generic equals(Object) contract: a null check on the argument, a type check, and a loop body that always exits on the empty-string fast path. It also encourages the reader to consider null-safety for the wrong side of the comparison.
s.length() == 0 reads the string’s count field via a method call and then does an integer compare. It is slightly noisier and expresses intent indirectly.

String.isEmpty() is a single-line, branchless check that reads exactly "is this string empty?" at the call site.

// Bad
if (s.equals("")) { ... }
if (s.length() == 0) { ... }

// Good
if (s.isEmpty()) { ... }

Remediation

Use String.isEmpty(). If the input may be null, combine with an explicit null check:

if (s != null && s.isEmpty()) { ... }

For the null-safe check "is this string null or empty?" prefer a small helper (for example Strings.hasText(s) already used in this codebase) instead of "".equals(s). The null-safe constant-on-the-left idiom (e.g. "foo".equals(s)) used to compare against a non-empty constant is fine and not flagged by this rule.

References

String.isEmpty()