How to convert string (IP numbers) to Integer in Java

Question

Example:

// using Integer.parseInt
int i = Integer.parseInt("123");

How would you do the same for?

// using Integer.parseInt
int i = Integer.parseInt("123.45.55.34");

Answer 1

The IPAddress Java library supports both IPv4 and IPv6 in a polymorphic manner. Disclaimer: I am the project manager of that library.

The following code works with both IPv4 and IPv6 addresses. Using your example IPv4 address:

IPAddress addr = new IPAddressString("123.45.55.34").getAddress();
BigInteger value = addr.getValue(); // 2066560802

If IPv4, you can just go straight to an int value:

if(addr.isIPv4()) {
    int val = addr.toIPv4().intValue(); // 2066560802
}

Answer 2

System.out.println(
        ByteBuffer.allocate(Integer.BYTES)
        .put(InetAddress.getByName("0.0.1.0").getAddress())
        .getInt(0));

Output:

256