题解 | #验证IP地址#TOP85

import java.util.*;


public class Solution {
    /**
     * 验证IP地址
     * @param IP string字符串 一个IP地址字符串
     * @return string字符串
     */
    public String solve (String IP) {
        // write code here
        if (IP == null || IP.length() < 1) {
            return "Neither";
        }
        char[] chars = IP.toCharArray();
        //1.先判断是 v4还是v6
        boolean isV4Type = false;
        for (char item : chars) {
            if (item == '.') {
                isV4Type = true;
                break;
            } else if (item == ':') {
                isV4Type = false;
                break;
            }
        }
        return isV4Type ? (isV4Validate(IP) ? "IPv4" : "Neither")
               : (isV6Valiedate(IP) ? "IPv6" : "Neither" );
    }

    private boolean isV4Validate(String ip) {
        String[] data = ip.split("\\.");
        if (data.length != 4) {
            return false;
        }
        for (String item : data) {
            if (item.length() > 1 && item.startsWith("0")) {
                return false;
            }
            try {
                int value = Integer.valueOf(item);
                if (value < 0 || value > 255) {
                    return false;
                }
            } catch (Exception e) {
                return false;
            }
        }
        return true;

    }

    private boolean isV6Valiedate(String ip) {
        char[] data = ip.toCharArray();
        int count = 0;
        for (char item : data) {
            if (item == ':') {
                if (count > 4 || count == 0) {
                    //每组有4个数
                    return false;
                }
                count = 0;
            } else {
                if ( !(item >= '0' && item <= '9' )
                        && !(item >= 'a' && item <= 'f')
                        && !(item >= 'A' && item <= 'F')) {
                    return false;
                } else {
                    count ++;
                }
            }
        }
        if(count == 0){
            //1db8:85a3:0:0:8A2E:0370:7334: 
            return false;
        }

        return true;
    }



}