how to get a byte[] representation from a IP in String form in Java

Question

Suppose I have the IP stored in a String:

String ip = "192.168.2.1"

and I want to get the byte array with the four ints. How can I do it? Thanks!

Solution 1

Something like this:

InetAddress ip = InetAddress.getByName("192.168.2.1");
byte[] bytes = ip.getAddress();
for (byte b : bytes) {
    System.out.println(b & 0xFF);
}

Solution 2

Each number is a byte, so in your case the appropriate byte[] would be { 192, 168, 2, 1 }.

To be more specific, if you have the string, you first have to split it by the "."s and then parse a byte from each resulting string.

Comments

[Inv3r53]

oh and btw the masking with 0xFF is for values over 127

[eternay]

A byte has a maximum value of 127. How can you put 192 in this array?

[Michael Campbell]

If only there were an unsigned byte type in java.

[RB_]

There is a library from google - Guava. Add it and use like this: import com.google.common.primitives.UnsignedBytes

[c.sankhala]

in this case, developer have to handle UnknownHostException

[Sam Ginrich]

@eternay it is (-64) & 0xFF == 192, -64 == (byte)192

[Denis]

The most efficient way. It needs only 4 bytes.

[The Corn Inspector]

I love this comment section, the most basic conversion and someone recommended using a library