I've got two ip addresses representing by String.

String first = "192.168.0.1";
String second = "192.168.0.5";

I need to sort it out like:

192.168.0.5
192.168.0.4
192.168.0.3
192.168.0.2

Here is my code so far:

 private static void method(String first, String second){
        String tempFirst = first.replace(".", "");
        String tempSecond = second.replace(".", "");
        int ipFirst = Integer.valueOf(tempFirst);
        int ipSecond = Integer.valueOf(tempSecond);

        while (ipSecond > ipFirst){
            System.out.println(ipSecond);
            ipSecond--;
        }
    }

I need to convert output from these method:

19216805
19216804
19216803
19216802

to:

192.168.0.5
192.168.0.4
192.168.0.3
192.168.0.2

How to achieve it?

CodePudding user response：

You can't. Does 19216802 mean 192.168.0.2 or 192.16.80.2?

An IP address can just be thought of as an unsigned 32bit number, so your 192.168.0.2 can be seen as 192 * 2 ^ 24 168 * 2 ^ 16 0 ^ 8 2 = 3232235522

What you really want to do is convert it to a 32bit number, sort, then convert back.

CodePudding user response：

My solution:

private static void ipAddress(String first, String second) throws UnknownHostException {
    byte[] bytesFirst = InetAddress.getByName(first).getAddress();
    byte[] bytesSecond = InetAddress.getByName(second).getAddress();
    int fIP = new BigInteger(1, bytesFirst).intValue();
    int sIP = new BigInteger(1, bytesSecond).intValue();

    while (sIP > fIP){
        int ip  = sIP ;
        String ipStr =
                String.format("%d.%d.%d.%d",
                        (ip >> 24 & 0xff),
                        (ip >> 16 & 0xff),
                        (ip >> 8 & 0xff),
                        (ip & 0xff));
        System.out.println(ipStr);
        sIP--;
    }
}

CodePudding user response：

I think the way you wish to achieve this is a bad way of doing it. My personal solution would be implement a class for Ip Addresses:

public class IpAddress implements Comparable<IpAddress> {
        public int A, B, C, D; // A.B.C.D (A,B,C,D are all 8 bit numbers)

        public IpAddress(String Ip) {
            this.A = Integer.valueOf(Ip.split("\\.")[0]);
            this.B = Integer.valueOf(Ip.split("\\.")[1]);
            this.C = Integer.valueOf(Ip.split("\\.")[2]);
            this.D = Integer.valueOf(Ip.split("\\.")[3]);
        }

        public int compareTo(IpAddress other) {
            return (this.A - other.A) * 16581375   (this.B - other.B) * 65025   (this.C - other.C) * 255   (this.D - other.D);
        }

        public String toString() {
            return this.A   "."   this.B   "."   this.C   "."   this.D;
        }

        public void decrement() {
            this.D--;
            if (this.D < 0) {
                this.D = 255;
                this.C--;
                if (this.C < 0) {
                this.C = 255;
                    this.B--;
                    if (this.B < 0) {
                        this.B = 255;
                        this.A--;
                        if (this.A < 0)
                            this.A = 255;
                    }
                }
            }
        }

        public boolean isGreaterThan(IpAddress other) {
            return (this.compareTo(other) > 0);
        }
  }

And for your method do:

private static void method(String first, String second){
    IpAddress ipFirst = new IpAddress(first);
    IpAddress ipSecond = new IpAddress(second);

    while (ipSecond.isGreaterThan(ipFirst)){
        System.out.println(ipSecond.toString());
        ipSecond.decrement();
    }
}