I have a program that will take a LAN IP provided, I then need to be able to modify just the last octet of the IP's, the first 3 will remain the same based on what was input in the LAN IP Text Field.
For example: User enter 192.168.1.97 as the LAN IP I need to be able to manipulate the last octet "97", how would I go about doing that so I can have another variable or string that would have say 192.168.1.100 or whatever else i want to set in the last octet.
String ip = "192.168.1.97";
// cut the last octet from ip (if you want to keep the . at the end, add 1 to the second parameter
String firstThreeOctets = ip.substring(0, ip.lastIndexOf(".")); // 192.168.1
String lastOctet = ip.substring(ip.lastIndexOf(".") + 1); // 97
Then, if you want to set the last octet to 100, simply do:
String newIp = firstThreeOctet + ".100"; // 192.168.1.100
You can use these methods
public static byte getLastOctet(String ip) {
String octet = ip.substring (ip.lastIndexOf('.') + 1);
return Byte.parseByte(octet);
}
public static String setLastOctet(String ip, byte octet) {
return ip.substring(0, ip.lastIndexOf ('.') + 1) + octet;
}
Replace the number at the end of the input.
String ipAddress = "192.168.1.97";
String newIpAddress = ipAddress.replaceFirst("\\d+$", "100")
You can do this with the IPAddress Java library as follows. Doing it this way validates the input string and octet value. Disclaimer: I am the project manager.
static IPv4Address change(String str, int lastOctet) {
IPv4Address addr = new IPAddressString(str).getAddress().toIPv4();
IPv4AddressSegment segs[] = addr.getSegments();
segs[segs.length - 1] = new IPv4AddressSegment(lastOctet);
return new IPv4Address(segs);
}
IPv4Address next = change("192.168.1.97", 100);
System.out.println(next);
Output:
192.168.1.100
