Is it necessary to close the StringReader in this case?

Question

Document doc = DocumentBuilderFactory.newInstance().
               newDocumentBuilder().
               parse(new InputSource(new StringReader(xml)));

Answer 1

StringReader extends Reader, which implements Closeable.
However, just by looking at the source code, you see what it does is basically irrelevant

public void close() {
    str = null;
}

InputSource doesn't implement Closeable or AutoCloseable, that means it is still the Reader duty to close itself. Another implementation of Reader might require that, however, so close it as standard.

One that might really require closing is FileReader, which is also acceptable by InputSource.