Program: 58239
Project: 58239
Buggy source:
public static void writeWithEditorKit(FileInfo info) throws FileAccessException, IOException {
  EditorCookie cookie=info.getCookie();
  StyledDocument openedDocument=cookie.openDocument();
  EditorKit kit=getEditorKit(info.getDataObject());
  try (InputStream is=new ByteArrayInputStream(info.getContentAsBytes())){
    final Caret caret=info.getCaret();
    if (caret == null) {
      LOG.log(Level.WARNING,"String_Node_Str");
      return;
    }
    int caretPosition=info.getCurrentCaretPosition();
    Runnable runner=() -> {
      NbDocument.runAtomic(openedDocument,() -> {
        try {
          cookie.getDocument().remove(0,cookie.getDocument().getLength());
          LOG.log(Level.INFO,"String_Node_Str",is);
          LOG.log(Level.INFO,"String_Node_Str",cookie.getDocument());
          kit.read(is,cookie.getDocument(),0);
          cookie.saveDocument();
          info.getFileObject().setAttribute(ENCODING_SETTING,info.getCharset().name());
          if (caretPosition < cookie.getDocument().getLength()) {
            LOG.log(Level.INFO,"String_Node_Str",new Object[]{info.getCaretOffset(),caretPosition,cookie.getDocument().getLength()});
            caret.setDot(caretPosition);
          }
          Reformat reformat=Reformat.get(cookie.getDocument());
          reformat.lock();
          try {
            reformat.reformat(0,cookie.getDocument().getLength());
          }
 catch (          BadLocationException ex) {
            LOG.log(Level.SEVERE,"String_Node_Str",ex.getMessage());
          }
 finally {
            reformat.unlock();
            cookie.saveDocument();
          }
        }
 catch (        BadLocationException|IOException ex) {
          LOG.log(Level.SEVERE,"String_Node_Str",ex.getMessage());
        }
      }
);
    }
;
    if (SwingUtilities.isEventDispatchThread()) {
      runner.run();
    }
 else {
      SwingUtilities.invokeLater(runner);
    }
  }
 catch (  IOException ex) {
    LOG.log(Level.SEVERE,"String_Node_Str",ex.getMessage());
  }
}

Fixed version (ground truth):
public static void writeWithEditorKit(FileInfo info) throws FileAccessException, IOException {
  EditorCookie cookie=info.getCookie();
  StyledDocument openedDocument=cookie.openDocument();
  EditorKit kit=getEditorKit(info.getDataObject());
  try (InputStream is=new ByteArrayInputStream(info.getContentAsBytes())){
    final Caret caret=info.getCaret();
    if (caret == null) {
      LOG.log(Level.WARNING,"String_Node_Str");
      return;
    }
    int caretPosition=info.getCurrentCaretPosition();
    Runnable runner=() -> {
      NbDocument.runAtomic(openedDocument,() -> {
        try {
          cookie.getDocument().remove(0,cookie.getDocument().getLength());
          LOG.log(Level.INFO,"String_Node_Str",is);
          LOG.log(Level.INFO,"String_Node_Str",cookie.getDocument());
          try (Reader reader=new InputStreamReader(is,info.getCharset())){
            kit.read(reader,cookie.getDocument(),0);
          }
           cookie.saveDocument();
          info.getFileObject().setAttribute(ENCODING_SETTING,info.getCharset().name());
          if (caretPosition < cookie.getDocument().getLength()) {
            LOG.log(Level.INFO,"String_Node_Str",new Object[]{info.getCaretOffset(),caretPosition,cookie.getDocument().getLength()});
            caret.setDot(caretPosition);
          }
          Reformat reformat=Reformat.get(cookie.getDocument());
          reformat.lock();
          try {
            reformat.reformat(0,cookie.getDocument().getLength());
          }
 catch (          BadLocationException ex) {
            LOG.log(Level.SEVERE,"String_Node_Str",ex.getMessage());
          }
 finally {
            reformat.unlock();
            cookie.saveDocument();
          }
        }
 catch (        BadLocationException|IOException ex) {
          LOG.log(Level.SEVERE,"String_Node_Str",ex.getMessage());
        }
      }
);
    }
;
    if (SwingUtilities.isEventDispatchThread()) {
      runner.run();
    }
 else {
      SwingUtilities.invokeLater(runner);
    }
  }
 catch (  IOException ex) {
    LOG.log(Level.SEVERE,"String_Node_Str",ex.getMessage());
  }
}