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    @Override
    public StringField removeLeadingZeros(StringField inputString) {
        String outputString;
        StringField outputStringField = new StringField();

        outputString = inputString.getValueAsString().replaceFirst("^0+(?!$)", "");
        outputStringField.setValue(outputString);

        return outputStringField;
    }

    @Override
    public StringField strReplace(StringField inputString, StringField old_char, StringField new_char) {
        String outputString;
        StringField outputStringField = new StringField();

        outputString = inputString.getValueAsString().replace(old_char.getValueAsString(), new_char.getValueAsString());
        outputStringField.setValue(outputString);

        return outputStringField;
    }