Parsing and verifying hex, octal and decimal numbers...

How to parse a number that might be octal, decimal or hexadecimal. Numbers like 0xFF, 0x1e, 077, -123, -0x12, -066. This must have been solved a million times, and here's my version:

Thank you for all the comments! My code is stupid! Use Long.decode(numberString).longValue() Instead!

String sign="";
int base=10;
if(numberString.startsWith("-")) {
    sign="-";
    numberString=numberString.substring(1);
}
if(numberString.startsWith("0x")) {
    numberString=numberString.substring(2);
    base=16;
} else if(numberString.startsWith("0") && numberString.length()>1) {
    numberString=numberString.substring(1);
    base=8;
}
return Long.parseLong(sign+numberString,base);

OK, and here is my VerifyListener:

class NumberVerifyer implements VerifyListener {
    final boolean fSigned;
    NumberVerifyer(boolean signed) {
        fSigned=signed;
    }
    public void verifyText(VerifyEvent e) {
        Text text = ((Text)e.widget);
        StringBuffer fulltext = new StringBuffer(text.getText());
        fulltext.replace(e.start, e.end, e.text);
        String sign=""; //$NON-NLS-1$
        if(fSigned)
            sign="-?"; //$NON-NLS-1$
        e.doit = fulltext.toString().matches(sign+"(0?|[1-9][0-9]*|0x[0-9a-fA-F]*|0[0-7]+)"); //$NON-NLS-1$
    }
}