String concatenation in loop

Reports String concatenation in loops.

As every String concatenation copies the whole string, usually it is preferable to replace it with explicit calls to StringBuilder.append() or StringBuffer.append().

Example:

String str = "";
for(int i=0; i<10; i++) {
  str += i;
}

After the quick-fix is applied:

String str = "";
StringBuilder strBuilder = new StringBuilder(str);
for(int i = 0; i<10; i++) {
  strBuilder.append(i);
}
str = strBuilder.toString();

Sometimes, the quick-fixes allow you to convert a String variable to a StringBuilder or introduce a new StringBuilder. Be careful if the original code specially handles the null value, as the replacement may change semantics. If null is possible, null-safe fixes that generate necessary null-checks are suggested. Also, it's not guaranteed that the automatic replacement will always be more performant.

Inspection Details
Available in:	IntelliJ IDEA 2023.3, Qodana for JVM 2023.3
Plugin:	Java, 233.SNAPSHOT

Last modified: 13 July 2023