CSSParser can work with different kinds of input by setting up an instance of class org.w3c.css.sac.InputSource in different ways.

String input

Working with strings as input is the simplest case because there is no need to take care of any encoding.

InputSource source = new InputSource(new StringReader("h1 { background: #ffcc44; }"));
CSSOMParser parser = new CSSOMParser(new SACParserCSS3());

CSSStyleSheet sheet = parser.parseStyleSheet(source, null, null);
....

Using an InputStreamReader

When using an InputStreamReader the reader itself is responsible for the correct conversion from the bytes (e.g. taken from a file) into characters. Therefore you have to provide the correct encoding as second parameter of the InputStreamReader constructor.

InputStream inStream = new FileInputStream("input.css");
try {
    InputSource source = new InputSource(new InputStreamReader(inStream, "UTF-8"));

    CSSOMParser parser = new CSSOMParser(new SACParserCSS3());
    ....
} finally {
    inStream.close();
}

Using an InputStream

If you like to use an InputStream as parser input, you have to inform the InputSource about the correct encoding of your input stream.

InputStream inStream = new FileInputStream("input.css");
try {
    InputSource source = new InputSource();
    source.setByteStream(inStream);
    source.setEncoding("UTF-8");

    CSSOMParser parser = new CSSOMParser(new SACParserCSS3());
    ....
} finally {
    inStream.close();
}