Not able to replace all for dollar sign

Question

can anyone advise why i encountered index out of bouns exception when running this method to replace the value by $ sign?

E.g. i pass in a message

Answer 1

After tinkering around with replaceAll() and never getting what I wanted I figured it would be easier to write a function to escape the dollar signs.

public static String escapeDollarSign(String value) {
    Pattern p = Pattern.compile("\\$");
    int off = 0;
    while (true) {
        Matcher m = p.matcher(value.substring(off));
        if (!m.find()) break;
        int moff = m.start();
        String left = value.substring(0, off+moff);
        String right = value.substring(off+moff+1, value.length());
        value = left+"\\$"+right;
        off += moff+1+1;
    }

    return value;
}

e.g.
$re$gex $can $ b$e a$ pain$
becomes
\$re\$gex \$can \$ b\$e a\$ pain\$