String concatenation as argument to 'StringBuilder.append()' call

Reports String concatenation used as the argument to StringBuffer.append(), StringBuilder.append() or Appendable.append().

Such calls may profitably be turned into chained append calls on the existing StringBuffer/Builder/Appendable saving the cost of an extra StringBuffer/Builder allocation. This inspection ignores compile-time evaluated String concatenations, in which case the conversion would only worsen performance.

Example:

  void bar(StringBuilder builder, String name) {
    builder.append("Hello," + name);    //warning
    builder.append("Hello," + "world"); //no warning
  }

Locating this inspection

By ID

Can be used to locate inspection in e.g. Qodana configuration files, where you can quickly enable or disable it, or adjust its settings.

StringConcatenationInsideStringBufferAppend

Via Settings dialog

Path to the inspection settings via IntelliJ Platform IDE Settings dialog, when you need to adjust inspection settings directly from your IDE.

Settings or Preferences | Editor | Inspections | Java | Performance

Suppressing Inspection

You can suppress this inspection by placing the following comment marker before the code fragment where you no longer want messages from this inspection to appear:

//noinspection StringConcatenationInsideStringBufferAppend

More detailed instructions as well as other ways and options that you have can be found in the product documentation:

IntelliJ IDEA 2025.2

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.2, Qodana for JVM 2025.2,

Last modified: 18 September 2025