diff --git a/mvvmhabit/src/main/java/me/goldze/mvvmhabit/utils/RegexUtils.java b/mvvmhabit/src/main/java/me/goldze/mvvmhabit/utils/RegexUtils.java
index 1da5ac6a..c6f0e3eb 100644
--- a/mvvmhabit/src/main/java/me/goldze/mvvmhabit/utils/RegexUtils.java
+++ b/mvvmhabit/src/main/java/me/goldze/mvvmhabit/utils/RegexUtils.java
@@ -1,6 +1,9 @@
 package me.goldze.mvvmhabit.utils;
 
+import android.support.v4.util.SimpleArrayMap;
+
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.regex.Matcher;
 import java.util.regex.Pattern;
@@ -13,6 +16,8 @@
  */
 public final class RegexUtils {
 
+    private final static SimpleArrayMap<String, String> CITY_MAP = new SimpleArrayMap<>();
+
     private RegexUtils() {
         throw new UnsupportedOperationException("u can't instantiate me...");
     }
@@ -22,136 +27,231 @@ private RegexUtils() {
     ///////////////////////////////////////////////////////////////////////////
 
     /**
-     * 验证手机号（简单）
+     * Return whether input matches regex of simple mobile.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isMobileSimple(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_MOBILE_SIMPLE, input);
     }
 
     /**
-     * 验证手机号（精确）
+     * Return whether input matches regex of exact mobile.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isMobileExact(final CharSequence input) {
-        return isMatch(RegexConstants.REGEX_MOBILE_EXACT, input);
+        return isMobileExact(input, null);
     }
 
     /**
-     * 验证电话号码
+     * Return whether input matches regex of exact mobile.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input       The input.
+     * @param newSegments The new segments of mobile number.
+     * @return {@code true}: yes<br>{@code false}: no
+     */
+    public static boolean isMobileExact(final CharSequence input, List<String> newSegments) {
+        boolean match = isMatch(RegexConstants.REGEX_MOBILE_EXACT, input);
+        if (match) return true;
+        if (newSegments == null) return false;
+        if (input == null || input.length() != 11) return false;
+        String content = input.toString();
+        for (char c : content.toCharArray()) {
+            if (!Character.isDigit(c)) {
+                return false;
+            }
+        }
+        for (String newSegment : newSegments) {
+            if (content.startsWith(newSegment)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Return whether input matches regex of telephone number.
+     *
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isTel(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_TEL, input);
     }
 
     /**
-     * 验证身份证号码15位
+     * Return whether input matches regex of id card number which length is 15.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isIDCard15(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_ID_CARD15, input);
     }
 
     /**
-     * 验证身份证号码18位
+     * Return whether input matches regex of id card number which length is 18.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isIDCard18(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_ID_CARD18, input);
     }
 
     /**
-     * 验证邮箱
+     * Return whether input matches regex of exact id card number which length is 18.
+     *
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
+     */
+    public static boolean isIDCard18Exact(final CharSequence input) {
+        if (isIDCard18(input)) {
+            int[] factor = new int[]{7, 9, 10, 5, 8, 4, 2, 1, 6, 3, 7, 9, 10, 5, 8, 4, 2};
+            char[] suffix = new char[]{'1', '0', 'X', '9', '8', '7', '6', '5', '4', '3', '2'};
+            if (CITY_MAP.isEmpty()) {
+                CITY_MAP.put("11", "北京");
+                CITY_MAP.put("12", "天津");
+                CITY_MAP.put("13", "河北");
+                CITY_MAP.put("14", "山西");
+                CITY_MAP.put("15", "内蒙古");
+
+                CITY_MAP.put("21", "辽宁");
+                CITY_MAP.put("22", "吉林");
+                CITY_MAP.put("23", "黑龙江");
+
+                CITY_MAP.put("31", "上海");
+                CITY_MAP.put("32", "江苏");
+                CITY_MAP.put("33", "浙江");
+                CITY_MAP.put("34", "安徽");
+                CITY_MAP.put("35", "福建");
+                CITY_MAP.put("36", "江西");
+                CITY_MAP.put("37", "山东");
+
+                CITY_MAP.put("41", "河南");
+                CITY_MAP.put("42", "湖北");
+                CITY_MAP.put("43", "湖南");
+                CITY_MAP.put("44", "广东");
+                CITY_MAP.put("45", "广西");
+                CITY_MAP.put("46", "海南");
+
+                CITY_MAP.put("50", "重庆");
+                CITY_MAP.put("51", "四川");
+                CITY_MAP.put("52", "贵州");
+                CITY_MAP.put("53", "云南");
+                CITY_MAP.put("54", "西藏");
+
+                CITY_MAP.put("61", "陕西");
+                CITY_MAP.put("62", "甘肃");
+                CITY_MAP.put("63", "青海");
+                CITY_MAP.put("64", "宁夏");
+                CITY_MAP.put("65", "新疆");
+
+                CITY_MAP.put("71", "台湾老");
+                CITY_MAP.put("81", "香港");
+                CITY_MAP.put("82", "澳门");
+                CITY_MAP.put("83", "台湾新");
+                CITY_MAP.put("91", "国外");
+            }
+            if (CITY_MAP.get(input.subSequence(0, 2).toString()) != null) {
+                int weightSum = 0;
+                for (int i = 0; i < 17; ++i) {
+                    weightSum += (input.charAt(i) - '0') * factor[i];
+                }
+                int idCardMod = weightSum % 11;
+                char idCardLast = input.charAt(17);
+                return idCardLast == suffix[idCardMod];
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Return whether input matches regex of email.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isEmail(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_EMAIL, input);
     }
 
     /**
-     * 验证URL
+     * Return whether input matches regex of url.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isURL(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_URL, input);
     }
 
     /**
-     * 验证汉字
+     * Return whether input matches regex of Chinese character.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isZh(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_ZH, input);
     }
 
     /**
-     * 验证用户名
-     * <p>取值范围为a-z,A-Z,0-9,"_",汉字，不能以"_"结尾,用户名必须是6-20位</p>
+     * Return whether input matches regex of username.
+     * <p>scope for "a-z", "A-Z", "0-9", "_", "Chinese character"</p>
+     * <p>can't end with "_"</p>
+     * <p>length is between 6 to 20</p>.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isUsername(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_USERNAME, input);
     }
 
     /**
-     * 验证yyyy-MM-dd格式的日期校验，已考虑平闰年
+     * Return whether input matches regex of date which pattern is "yyyy-MM-dd".
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isDate(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_DATE, input);
     }
 
     /**
-     * 验证IP地址
+     * Return whether input matches regex of ip address.
      *
-     * @param input 待验证文本
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isIP(final CharSequence input) {
         return isMatch(RegexConstants.REGEX_IP, input);
     }
 
     /**
-     * 判断是否匹配正则
+     * Return whether input matches the regex.
      *
-     * @param regex 正则表达式
-     * @param input 要匹配的字符串
-     * @return {@code true}: 匹配<br>{@code false}: 不匹配
+     * @param regex The regex.
+     * @param input The input.
+     * @return {@code true}: yes<br>{@code false}: no
      */
     public static boolean isMatch(final String regex, final CharSequence input) {
         return input != null && input.length() > 0 && Pattern.matches(regex, input);
     }
 
     /**
-     * 获取正则匹配的部分
+     * Return the list of input matches the regex.
      *
-     * @param regex 正则表达式
-     * @param input 要匹配的字符串
-     * @return 正则匹配的部分
+     * @param regex The regex.
+     * @param input The input.
+     * @return the list of input matches the regex
      */
     public static List<String> getMatches(final String regex, final CharSequence input) {
-        if (input == null) return null;
+        if (input == null) return Collections.emptyList();
         List<String> matches = new ArrayList<>();
         Pattern pattern = Pattern.compile(regex);
         Matcher matcher = pattern.matcher(input);
@@ -162,40 +262,50 @@ public static List<String> getMatches(final String regex, final CharSequence inp
     }
 
     /**
-     * 获取正则匹配分组
+     * Splits input around matches of the regex.
      *
-     * @param input 要分组的字符串
-     * @param regex 正则表达式
-     * @return 正则匹配分组
+     * @param input The input.
+     * @param regex The regex.
+     * @return the array of strings computed by splitting input around matches of regex
      */
     public static String[] getSplits(final String input, final String regex) {
-        if (input == null) return null;
+        if (input == null) return new String[0];
         return input.split(regex);
     }
 
     /**
-     * 替换正则匹配的第一部分
+     * Replace the first subsequence of the input sequence that matches the
+     * regex with the given replacement string.
      *
-     * @param input       要替换的字符串
-     * @param regex       正则表达式
-     * @param replacement 代替者
-     * @return 替换正则匹配的第一部分
+     * @param input       The input.
+     * @param regex       The regex.
+     * @param replacement The replacement string.
+     * @return the string constructed by replacing the first matching
+     * subsequence by the replacement string, substituting captured
+     * subsequences as needed
      */
-    public static String getReplaceFirst(final String input, final String regex, final String replacement) {
-        if (input == null) return null;
+    public static String getReplaceFirst(final String input,
+                                         final String regex,
+                                         final String replacement) {
+        if (input == null) return "";
         return Pattern.compile(regex).matcher(input).replaceFirst(replacement);
     }
 
     /**
-     * 替换所有正则匹配的部分
+     * Replace every subsequence of the input sequence that matches the
+     * pattern with the given replacement string.
      *
-     * @param input       要替换的字符串
-     * @param regex       正则表达式
-     * @param replacement 代替者
-     * @return 替换所有正则匹配的部分
+     * @param input       The input.
+     * @param regex       The regex.
+     * @param replacement The replacement string.
+     * @return the string constructed by replacing each matching subsequence
+     * by the replacement string, substituting captured subsequences
+     * as needed
      */
-    public static String getReplaceAll(final String input, final String regex, final String replacement) {
-        if (input == null) return null;
+    public static String getReplaceAll(final String input,
+                                       final String regex,
+                                       final String replacement) {
+        if (input == null) return "";
         return Pattern.compile(regex).matcher(input).replaceAll(replacement);
     }
 }