Convert IP between IPv4 and numerical format in java

Question

An IPv4 can have more representations: as string (a.b.c.d) or numerical (as an unsigned int of 32 bits). (Maybe other, but I will ignore them.)

Is there any built in support in Java (8), simple and easy to use, without network access, to convert between these formats?

I need something like this:

long ip = toNumerical("1.2.3.4"); // returns 0x0000000001020304L
String ipv4 = toIPv4(0x0000000001020304L); // returns "1.2.3.4"

If there is no built in such functions in Java, feel free to suggest other solutions.

Thank you

Answer 1

The can be done using InetAddress as follows.

//Converts a String that represents an IP to an int.
InetAddress i = InetAddress.getByName(IPString);
int intRepresentation = ByteBuffer.wrap(i.getAddress()).getInt();

//This converts an int representation of ip back to String
i = InetAddress.getByName(String.valueOf(intRepresentation));
String ip = i.getHostAddress();

Answer 2

Heres is a way to Convert IP to Number. I found it a valid way to accomplish the task in Java.

public long ipToLong(String ipAddress) {

    String[] ipAddressInArray = ipAddress.split("\\.");

    long result = 0;
    for (int i = 0; i < ipAddressInArray.length; i++) {

        int power = 3 - i;
        int ip = Integer.parseInt(ipAddressInArray[i]);
        result += ip * Math.pow(256, power);

    }

    return result;
  }

This is also how you would implement it in Scala.

  def convertIPToLong(ipAddress: String): Long = {

    val ipAddressInArray = ipAddress.split("\\.")
    var result = 0L

    for (i  <- 0  to ipAddressInArray.length-1) {
      val power = 3 - i
      val ip = ipAddressInArray(i).toInt
      val longIP = (ip * Math.pow(256, power)).toLong
      result = result +longIP
    }
    result
  }