FULL PRODUCT VERSION :
java version "1.6.0_06"
Java(TM) SE Runtime Environment (build 1.6.0_06-b02)
Java HotSpot(TM) Client VM (build 10.0-b22, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows XP [Version 5.1.2600]

EXTRA RELEVANT SYSTEM CONFIGURATION :
Service Pack 3

A DESCRIPTION OF THE PROBLEM :
If a StyledDocument is got from a JTextPane initialized from a string that contains "\r\n" characters, then String#substring != StyledDocument#getText for the same indices, provided they are greater than the index of the first "\r\n".

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
the result of StyledDocument#getText is the same as the result String#substring
ACTUAL -
the result of StyledDocument#getText is different than the result String#substring

REPRODUCIBILITY :
This bug can be reproduced always.

---------- BEGIN SOURCE ----------
public static void main(String[] args) throws BadLocationException {
        // not ok
        String s = "01234\r\n7890";
        JTextPane pane = new JTextPane();
        pane.setText(s);
        StyledDocument doc = pane.getStyledDocument();
        assert s.length() == doc.getLength();
        System.out.println(s.substring(7, 10));
        System.out.println(doc.getText(7, 10 - 7));
 
        // ok
        s = "01234\n67890";
        pane.setText(s);
        doc = pane.getStyledDocument();
        assert s.length() == doc.getLength();
        System.out.println(s.substring(7, 10));
        System.out.println(doc.getText(7, 10 - 7));
    }
---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
replace "\r\n" with "\n" when constructing the JTextPane