Jmeter, over writing data to file if it exists using jsr223 postProcessor

def file= new File(path + 'fileName.csv');
        List.unique().each { element ->
                file<< element << newLine
                }

Now the script is appending the file But i want to clear all the data and over write the fileName.csv if it already exists If the file doesn't exists, create the file and write data to file.