public static IpPrefix valueOf(int address, int prefixLength) {
        return new IpPrefix(IpAddress.valueOf(address), prefixLength);
    }
@Test(expected = IllegalArgumentException.class)
    public void testInvalidValueOfIntegerNegativePrefixLengthIPv4() {
        IpPrefix ipPrefix;

        ipPrefix = IpPrefix.valueOf(0x01020304, -1);
    }