You can construct an InputStreamReader from that InputStream

new InputStreamReader(myInputStream, encoding)

Where myInputStream is your InputStream and encoding is a String that defines the encoding used by your datasource.

You can call your CSVReader like this:

new CSVReader(new InputStreamReader(myInputStream, encoding));

Use

CSVReader reader = new CSVReader(new InputStreamReader(input));

Edit to answer the comment

The problem is because you don't have any constructor for FileReader as you want. See the FileReader API for details. But since you will have to convert the byte stream to character stream so you will have to use InputStreamReader. For better performance you can wrap it with a BufferedReader also

First, you should try uniVocity-parsers CSV parser as it is twice as fast and has many additional features.

Sencond, you should provide the encoding of your input.

Third, you may also need to specify the line separators explicitly

Example using uniVocity-parsers:

File initialFile = new File("/Users/me/Downloads/file.csv");
InputStream targetStream = FileUtils.openInputStream(initialFile);

CsvParserSettings settings = new CsvParserSettings();
settings.getFormat().setLineSeparator("\n");

CsvParser parser = new CsvParser(settings);
List<String[]> allRows = parser.parseAll(new InputStreamReader(targetStream, "UTF-8"));

Disclosure: I am the author of this library. It's open-source and free (Apache V2.0 license).