求个拆分IP地址的算法,该怎么解决

public static void main(String[] args) {        List<String> list = new ArrayList<String>();        list.add("221.226.83.9");        list.add("221.226.83.10");        list.add("221.226.83.11");        list.add("221.224.83.53");        list.add("221.224.83.52");        list.add("221.226.87.21");        list.add("221.226.87.22");        Set<String> set = new TreeSet<String>(new Comparator<String>(){            public int compare(String arg0, String arg1){                String[] key1 = arg0.split("\\.");                String[] key2 = arg1.split("\\.");                for(int i= 0;i<key1.length;i++){                    if(Integer.parseInt(key1[i]) == Integer.parseInt(key2[i])){                        continue;                    }                    if(Integer.parseInt(key1[i]) > Integer.parseInt(key2[i])){                        return 1;                    }                    if(Integer.parseInt(key1[i]) < Integer.parseInt(key2[i])){                        return -1;                    }                }                return 0;            }});        set.addAll(list);        System.out.println(set);        List<String> result = new ArrayList<String>();        String s1 = null;        String s2 = null;        String start = null;        String end = null;        int count = 0;        for(String s : set){            count ++;            if(s1==null){                s1 = s;                start = s;            }            else{                s2 = s;                if(s2.startsWith(s1.substring(0,s1.lastIndexOf(".")))&&                        Integer.parseInt(s2.substring(s2.lastIndexOf(".")+1))                             - Integer.parseInt(s1.substring(s1.lastIndexOf(".")+1)) == 1){                    end = s;                    s1 = s2;                }                                else{                    result.add(start + (end==null?"":"-"+end));                    s1 = s;                    start = s;                    end = null;                }                                if(count == set.size()){                    result.add(start+ (end==null?"":"-"+end));                    s1=null;                    end =null;                }            }        }        System.out.println(result);    }
------解决方案--------------------
Java code
import java.util.HashMap;import java.util.List;import java.util.Map;public class Test03 {    private static List<String> IP_LIST = new ArrayList<String>();    static {        IP_LIST.add("221.226.83.50");        IP_LIST.add("221.226.83.51");        IP_LIST.add("221.226.83.52");        IP_LIST.add("221.226.83.53");        IP_LIST.add("221.226.83.54");        IP_LIST.add("221.226.83.55");        IP_LIST.add("221.226.83.61");        IP_LIST.add("221.226.83.62");        IP_LIST.add("221.226.83.63");        IP_LIST.add("221.226.83.64");        IP_LIST.add("221.226.83.75");        IP_LIST.add("221.226.83.255");        IP_LIST.add("221.226.84.1");        IP_LIST.add("221.226.84.2");        IP_LIST.add("221.226.84.3");        IP_LIST.add("221.226.85.4");    }    public static void main(String[] args) {        List<String> list = getIPList(IP_LIST);        for (String str : list) {            System.out.println(str);        }    }    public static List<String> getIPList(List<String> ipList) {        Map<String, List<Integer>> map = new HashMap<String, List<Integer>>();        for (String ip : ipList) {            int index = ip.lastIndexOf('.');            String ip123 = ip.substring(0, index + 1);            int ip4 = Integer.valueOf(ip.substring(index + 1, ip.length()));            if (map.containsKey(ip123)) {                map.get(ip123).add(ip4);            } else {                List<Integer> ip4List = new ArrayList<Integer>();                ip4List.add(ip4);                map.put(ip123, ip4List);            }        }        List<String> list = new ArrayList<String>();        for (Map.Entry<String, List<Integer>> entry : map.entrySet()) {            String ip123 = entry.getKey();            List<Integer> ip4List = entry.getValue();            Collections.sort(ip4List);            int len = ip4List.size();            for (int i = 0; i < len; i++) {                int start = ip4List.get(i);                int stop = start;                while (++i < len) {                    int current = ip4List.get(i);                    if (current == (stop + 1)) {                        stop = current;                    } else {                        list.add(start == stop ? ip123 + String.valueOf(start)                                : ip123 + String.valueOf(start) + "-" + ip123                                        + String.valueOf(stop));                        i--;                        break;                    }                }                if (i >= len) {                    list.add(start == stop ? ip123 + String.valueOf(start)                            : ip123 + String.valueOf(start) + "-" + ip123                                    + String.valueOf(stop));                }            }        }        return list;    }}