Path Traversal vulnerability for a file object

I'm trying to fix Path Traversal Vulnerability raised by Gitlab SAST in the Java Source code. There is a scenario where I am creating a file object by passing in an Input string. Then creating a file output stream to write to the file represented by the specified File object.

private BufferedWriter createFile( String filePath, String fileName )
    {       
        try {
            File dir = new File( FilenameUtils.normalize(filePath) );
    
            if ( ! dir.exists() ) {
                if (! dir.mkdirs() ) {
                    log("** WARNING: The file " + fileName + " cannot be created because the path " + filePath  + " could not be created **\n");
                    return null;
                }
            }
        
            File file = new File(dir.getPath() + File.separatorChar + fileName);
            if ( file.exists() )
                file.delete();

            FileOutputStream fos = new FileOutputStream( file , false );
            ps = new PrintStream(fos);
            
            return new BufferedWriter(new FileWriter(file));
        }
        catch (Exception e) {
            log("** Warning: could not create file : " + filePath + File.separatorChar + fileName + " **\n");
            e.printStackTrace();
            return null;
        }
    }

Issue is I am getting Path traversal vulnerability error for line FileOutputStream fos = new FileOutputStream( file , false ); How do I fix this? I have tried using getCanonicalPath() method but that didn't solve the issue.

There was a vulnerability error while creating file object as well which I fixed it using FilenameUtils class