StringBuffer/StringBuilder for Constant Value
ID |
java.stringbuffer_for_constant_value |
Severity |
info |
Remediation Complexity |
trivial |
Remediation Risk |
low |
Remediation Effort |
low |
Resource |
Efficiency |
Language |
Java |
Tags |
best-practice, efficiency |
Description
Reports local StringBuffer or StringBuilder variables that are never mutated. When no mutator method (append, insert, delete, replace, reverse, setCharAt, setLength, deleteCharAt, appendCodePoint) is called on the variable, a plain String would suffice and avoids the overhead of maintaining a mutable buffer object.
Rationale
String objects are immutable and cheap to create, while StringBuffer and StringBuilder carry the overhead of a resizable character array and synchronization (for StringBuffer). If the buffer is never modified after construction, using it is wasteful.
// Bad -- StringBuffer is never mutated
StringBuffer sb = new StringBuffer("Hello");
String result = sb.toString();A buffer that is handed to something else — passed as an argument, returned, stored in a field or added to a collection — is not reported: the receiver may append to it out of sight, so "never mutated" is no longer decidable from the declaring method alone.
// Not reported -- the helper appends to the buffer
StringBuilder sb = new StringBuilder("{");
addField(sb, "\"login\": ", login);
return sb.toString();Remediation
Replace the StringBuffer/StringBuilder with a plain String.
// Good -- use String directly
String result = "Hello";