public static PennTreebankPOS tag(String word) {
        for (int i = 0; i < REGEX.length; i++) {
            if (REGEX[i].matcher(word).matches()) {
                return REGEX_POS[i];
            }
        }

        return null;
    }
@Test
    public void testTag() {
        System.out.println("tag");
        assertEquals(PennTreebankPOS.CD, RegexPOSTagger.tag("123"));
        assertEquals(PennTreebankPOS.CD, RegexPOSTagger.tag("1234567890"));
        assertEquals(PennTreebankPOS.CD, RegexPOSTagger.tag("123.45"));
        assertEquals(PennTreebankPOS.CD, RegexPOSTagger.tag("1,234"));
        assertEquals(PennTreebankPOS.CD, RegexPOSTagger.tag("1,234.5678"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("914-544-3333"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("544-3333"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("x123"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("x123"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("http://www.msnbc.msn.com/id/42231726/?GT1=43001"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("ftp://www.msnbc.msn.com/id/42231726/?GT1=43001"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("nobody@usc.edu"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("no.body@usc.edu.cn"));
        assertEquals(PennTreebankPOS.NN, RegexPOSTagger.tag("no_body@usc.edu.cn"));
    }