Redundant String.substring(0)

java.string_substring_zero

Severity

info

Remediation Complexity

trivial

Remediation Risk

low

Remediation Effort

low

Resource

Best Practice

Language

Java

Description

Reports calls to String.substring(0) — the one-argument overload with a start index of zero.

Rationale

String.substring(int beginIndex) returns the tail of the string starting at the given index. With beginIndex == 0 the returned value is the original string itself — the JDK short-circuits the call and simply returns this. The expression is therefore a no-op that adds a method frame and a reader-distracting step without changing behaviour. Deleting it makes the intent (or lack thereof) clear.

// Bad — no-op substring
String copy = s.substring(0);

// Good — use the string directly
String copy = s;

Remediation

Remove the .substring(0) call. If the original goal was to make an explicit copy for some downstream API, confirm that the copy is actually needed — String is immutable, so a copy is almost never required.

References

String.substring(int)