#vulnerable code 
                                @Test
    public void testIPv6Check() {
        byte[] nonInternalIp = UtilAll.string2bytes("24084004018081003FAA1DDE2B3F898A");
        byte[] internalIp = UtilAll.string2bytes("FEC0000000000000000000000000FFFF");
        assertThat(UtilAll.isInternalV6IP(nonInternalIp)).isFalse();
        assertThat(UtilAll.isInternalV6IP(internalIp)).isTrue();
        assertThat(UtilAll.ipToIPv6Str(nonInternalIp).toUpperCase()).isEqualTo("2408:4004:0180:8100:3FAA:1DDE:2B3F:898A");
    } 
                            #location 6 
                            #vulnerability type NULL_DEREFERENCE
#fixed code
                                @Test
    public void testIPv6Check() throws UnknownHostException {
        InetAddress nonInternal = InetAddress.getByName("2408:4004:0180:8100:3FAA:1DDE:2B3F:898A");
        InetAddress internal = InetAddress.getByName("FE80:0000:0000:0000:0000:0000:0000:FFFF");
        assertThat(UtilAll.isInternalV6IP(nonInternal)).isFalse();
        assertThat(UtilAll.isInternalV6IP(internal)).isTrue();
        assertThat(UtilAll.ipToIPv6Str(nonInternal.getAddress()).toUpperCase()).isEqualTo("2408:4004:0180:8100:3FAA:1DDE:2B3F:898A");
    }