IP地址的哈希函数

Question

I need to generate a unique ID(a string) from a ip address and vice-versa. The unique Id must be of 8-9 character. Is there any has function which could do that in java?

Answer 1

Since an IPv4 Address consists of 4 Bytes, you could simply use the hex representation, which would result in 8 characters

This could be an implementation:

public static String ipToId(String ip) {
    return Arrays.stream(ip.split("\\."))
        .map(Integer::parseInt)
        .map(number -> String.format("%02X", number))
        .collect(Collectors.joining());
}

The reverse could be done via:

public static String idToIp( String id )
{
    return Stream.of( id )
            .map( Base64.getDecoder()::decode )
            .flatMapToInt( bytes -> IntStream.range( 0, bytes.length )
                    .map( index -> bytes[index] & 0xFF ) )
            .mapToObj( String::valueOf )
            .collect( Collectors.joining( "." ) );
}