Question

In Java, i have an arrayList of ip address. how do i find the min and max ?

I have used the Collection.min() but it doesnt work given a case like :

192.168.0.1  <--min 
192.168.0.250
192.168.0.9  <--max

how do i return

192.168.0.1  <--min
192.168.0.250 <--max

instead?

---

ArrayList is retrieve from the database. I would need to do this operation per tick (each tick is at 5 sec interval). The number of IP address would hit a max of probably 300.

Answer 1

Referring to Java – IP Address to Integer and back

public static String intToIp(int i) {
    return ((i >> 24 ) & 0xFF) + "." +
           ((i >> 16 ) & 0xFF) + "." +
           ((i >>  8 ) & 0xFF) + "." +
           ( i        & 0xFF);
}

public static Long ipToInt(String addr) {
    String[] addrArray = addr.split("\\.");

    long num = 0;
    for (int i=0;i<addrArray.length;i++) {
        int power = 3-i;

        num += ((Integer.parseInt(addrArray[i])%256 * Math.pow(256,power)));
    }
    return num;
}

Retrieving from the database the Ip address String, I converted all to a ArrayList and then apply the Collection.min()
Then I convert back the long to int and then back to String. To obtain a sorted String of ip addresses.

Thanks