18. Commenter

A commenter enables the user to comment-out a line of code at the cursor or selected code automatically. The Commenter defines support for Code | Comment with Line Comment and Code | Comment with Block Comment actions.

Define a Commenter

The SimpleCommenter for Simple Language defines the line comment prefix as #.

final class SimpleCommenter implements Commenter {

  @Override
  public String getLineCommentPrefix() {
    return "#";
  }

  @Override
  public String getBlockCommentPrefix() {
    return "";
  }

  @Nullable
  @Override
  public String getBlockCommentSuffix() {
    return null;
  }

  @Nullable
  @Override
  public String getCommentedBlockCommentPrefix() {
    return null;
  }

  @Nullable
  @Override
  public String getCommentedBlockCommentSuffix() {
    return null;
  }

}

Register the Commenter

The SimpleCommenter implementation is registered in the plugin configuration file using the com.intellij.lang.commenter extension point.

<extensions defaultExtensionNs="com.intellij">
  <lang.commenter
      language="Simple"
      implementationClass="org.intellij.sdk.language.SimpleCommenter"/>
</extensions>

Run the Project

Run the plugin.

Open the example Simple Language properties file in the IDE Development Instance. Place the cursor at the website line. Select Code | Comment with Line Comment. The line is converted to a comment. Select Code | Comment with Line Comment again, and the comment is converted back to active code.

21 July 2026