Substring Then Search
ID |
java.substring_then_search |
Severity |
low |
Remediation Complexity |
trivial |
Remediation Risk |
low |
Remediation Effort |
low |
Resource |
Efficiency |
Language |
Java |
Tags |
efficiency |
Description
Reports a call chain str.substring(beginIndex).m(..) where m is indexOf(int), indexOf(String) or startsWith(String).
Rationale
Each of these three methods has an overload that accepts a starting offset directly. Calling substring(beginIndex) first allocates a new String holding the remainder, purely so the search method can be called on it — an allocation, and a full character copy, that buys nothing.
// Bad - allocates a new String just to search inside it
int found = str.substring(beginIndex).indexOf('x');Remediation
Call the offset-taking overload directly on the original String. For indexOf, subtract beginIndex from the result to get the same index as before.
// Good - no extra allocation; same result once the offset is added back
int found = str.indexOf('x', beginIndex);
if (found >= 0) {
found -= beginIndex;
}