'StringBuilder.append(CharArray, offset, len)' call on the JVM

Reports a StringBuilder.append(CharArray, offset, len) function call on the JVM platform that should be replaced with a StringBuilder.appendRange(CharArray, startIndex, endIndex) function call.

The append function behaves differently on the JVM, JS and Native platforms, so using the appendRange function is recommended.

Example:

  fun f(charArray: CharArray, offset: Int, len: Int): String {
      return buildString {
          append(charArray, offset, len)
      }
  }

After the quick-fix is applied:

  fun f(charArray: CharArray, offset: Int, len: Int): String {
      return buildString {
          appendRange(charArray, offset, offset + len)
      }
  }

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.

ReplaceWithStringBuilderAppendRange

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 | Kotlin | Other problems

Inspection ID: ReplaceWithStringBuilderAppendRange

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 ReplaceWithStringBuilderAppendRange

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

IntelliJ IDEA 2025.3

Inspection Details
By default bundled with:	IntelliJ IDEA 2025.3, Qodana for JVM 2025.3,

Last modified: 03 December 2025