Program: 120180
Project: 120180
Buggy source:
@Override protected boolean checkFieldsValue(){
  boolean editable=jsonFilePath.getEditable();
  StringBuffer msgError=new StringBuffer();
  if (creation && !noFileButton.getSelection() && !useFileButton.getSelection()) {
    msgError.append("String_Node_Str");
  }
  if (creation && editable && jsonFilePath.getText() == "String_Node_Str") {
    msgError.append("String_Node_Str");
  }
  if (!valid && creation) {
    String JSONXsdText=jsonFilePath.getText();
    if (JSONXsdText != null && !"String_Node_Str".equals(JSONXsdText)) {
      if (isContextMode()) {
        ContextType contextType=ConnectionContextHelper.getContextTypeForContextMode(connectionItem.getConnection());
        JSONXsdText=TalendQuoteUtils.removeQuotes(ConnectionContextHelper.getOriginalValue(contextType,jsonFilePath.getText()));
      }
      msgError.append(JSONXsdText + "String_Node_Str");
    }
  }
  String text=outputFilePath.getText();
  if (isContextMode()) {
    ContextType contextType=ConnectionContextHelper.getContextTypeForContextMode(connectionItem.getConnection(),true);
    text=TalendQuoteUtils.removeQuotes(ConnectionContextHelper.getOriginalValue(contextType,text));
  }
  if (text != null && !text.equals("String_Node_Str") && !isJSONFile(text)) {
    msgError.append("String_Node_Str");
  }
  if ("String_Node_Str".equals(msgError.toString())) {
    updateStatus(IStatus.OK,null);
    return true;
  }
  updateStatus(IStatus.ERROR,msgError.toString());
  return false;
}

Fixed version (ground truth):
@Override protected boolean checkFieldsValue(){
  String jsonFilePathText=jsonFilePath.getText();
  String outputFilePathText=outputFilePath.getText();
  boolean editable=jsonFilePath.getEditable();
  StringBuffer msgError=new StringBuffer();
  if (creation && !noFileButton.getSelection() && !useFileButton.getSelection()) {
    msgError.append("String_Node_Str");
  }
  if (creation && editable && jsonFilePathText == "String_Node_Str") {
    msgError.append("String_Node_Str");
  }
  if (!valid && creation) {
    if (jsonFilePathText != null && !"String_Node_Str".equals(jsonFilePathText)) {
      if (isContextMode()) {
        ContextType contextType=ConnectionContextHelper.getContextTypeForContextMode(connectionItem.getConnection());
        jsonFilePathText=TalendQuoteUtils.removeQuotes(ConnectionContextHelper.getOriginalValue(contextType,jsonFilePathText));
      }
      msgError.append(jsonFilePathText + "String_Node_Str");
    }
  }
  if (isContextMode()) {
    ContextType contextType=ConnectionContextHelper.getContextTypeForContextMode(connectionItem.getConnection(),true);
    outputFilePathText=TalendQuoteUtils.removeQuotes(ConnectionContextHelper.getOriginalValue(contextType,outputFilePathText));
  }
  if (jsonFilePathText != null && !jsonFilePathText.equals("String_Node_Str")) {
    File file=new File(jsonFilePathText);
    if (!file.exists() || !isJSONFile(jsonFilePathText)) {
      msgError.append("String_Node_Str");
    }
  }
  if (outputFilePathText != null && !outputFilePathText.equals("String_Node_Str") && !isJSONFile(outputFilePathText)) {
    msgError.append("String_Node_Str");
  }
  if ("String_Node_Str".equals(msgError.toString())) {
    updateStatus(IStatus.OK,null);
    return true;
  }
  updateStatus(IStatus.ERROR,msgError.toString());
  return false;
}