Non-constant 'String' can be replaced with 'StringBuilder'

Reports variables declared as java.lang.String that are repeatedly appended to. Such variables could be declared more efficiently as java.lang.StringBuffer or java.lang.StringBuilder.

Example:

String s = "";
for (int i = 0; i < names.length; i++) {
  String name = names[i] + (i == names.length - 1 ? "" : " ");
  s = s + name;
}

Such a loop can be replaced with:

StringBuilder s = new StringBuilder();
for (int i = 0; i < names.length; i++) {
  String name = names[i] + (i == names.length - 1 ? "" : " ");
  s.append(name);
}

Or even with:

String s = String.join(" ", names);

Use the option to make this inspection only report when the variable is appended to in a loop.

Inspection options

Option	Type	Default
Only warn when appending in a loop	Checkbox	true

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

Last modified: 13 July 2023