StringUtils

public class StringUtils {


    private StringUtils() {
        throw new AssertionError();
    }

    /**
     * is null or its length is 0 or it is made by space
     * 

     * 
     * isBlank(null) = true;
     * isBlank("") = true;
     * isBlank("  ") = true;
     * isBlank("a") = false;
     * isBlank("a ") = false;
     * isBlank(" a") = false;
     * isBlank("a b") = false;
     * 
     *
     * @param str
     * @return if string is null or its size is 0 or it is made by space, return true, else return false.
     */
    public static boolean isBlank(String str) {
        return (str == null || str.trim().length() == 0);
    }

    /**
     * is null or its length is 0
     * 

     * 
     * isEmpty(null) = true;
     * isEmpty("") = true;
     * isEmpty("  ") = false;
     * 
     *
     * @param str
     * @return if string is null or its size is 0, return true, else return false.
     */
    public static boolean isEmpty(CharSequence str) {
        return (str == null || str.length() == 0);
    }

    /**
     * compare two string
     *
     * @param actual
     * @param expected
     * @return
     * @see ObjectUtils#isEquals(Object, Object)
     */
    public static boolean isEquals(String actual, String expected) {
        return actual == expected || (actual == null ? expected == null : actual.equals(expected));
    }

    /**
     * get length of CharSequence
     * 

     * 
     * length(null) = 0;
     * length(\"\") = 0;
     * length(\"abc\") = 3;
     * 
     *
     * @param str
     * @return if str is null or empty, return 0, else return {@link CharSequence#length()}.
     */
    public static int length(CharSequence str) {
        return str == null ? 0 : str.length();
    }

    /**
     * null Object to empty string
     * 

     * 
     * nullStrToEmpty(null) = "";
     * nullStrToEmpty("") = "";
     * nullStrToEmpty("aa") = "aa";
     * 
     *
     * @param str
     * @return
     */
    public static String nullStrToEmpty(Object str) {
        return (str == null ? "" : (str instanceof String ? (String) str : str.toString()));
    }

    /**
     * capitalize first letter
     * 

     * 
     * capitalizeFirstLetter(null)     =   null;
     * capitalizeFirstLetter("")       =   "";
     * capitalizeFirstLetter("2ab")    =   "2ab"
     * capitalizeFirstLetter("a")      =   "A"
     * capitalizeFirstLetter("ab")     =   "Ab"
     * capitalizeFirstLetter("Abc")    =   "Abc"
     * 
     *
     * @param str
     * @return
     */
    public static String capitalizeFirstLetter(String str) {
        if (isEmpty(str)) {
            return str;
        }

        char c = str.charAt(0);
        return (!Character.isLetter(c) || Character.isUpperCase(c)) ? str : new StringBuilder(str.length())
                .append(Character.toUpperCase(c)).append(str.substring(1)).toString();
    }

    /**
     * encoded in utf-8
     * 

     * 
     * utf8Encode(null)        =   null
     * utf8Encode("")          =   "";
     * utf8Encode("aa")        =   "aa";
     * utf8Encode("啊啊啊啊")   = "%E5%95%8A%E5%95%8A%E5%95%8A%E5%95%8A";
     * 
     *
     * @param str
     * @return
     * @throws UnsupportedEncodingException if an error occurs
     */
    public static String utf8Encode(String str) {
        if (!isEmpty(str) && str.getBytes().length != str.length()) {
            try {
                return URLEncoder.encode(str, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                throw new RuntimeException("UnsupportedEncodingException occurred. ", e);
            }
        }
        return str;
    }

    /**
     * encoded in utf-8, if exception, return defultReturn
     *
     * @param str
     * @param defultReturn
     * @return
     */
    public static String utf8Encode(String str, String defultReturn) {
        if (!isEmpty(str) && str.getBytes().length != str.length()) {
            try {
                return URLEncoder.encode(str, "UTF-8");
            } catch (UnsupportedEncodingException e) {
                return defultReturn;
            }
        }
        return str;
    }

    /**
     * get innerHtml from href
     * 

     * 
     * getHrefInnerHtml(null)                                  = ""
     * getHrefInnerHtml("")                                    = ""
     * getHrefInnerHtml("mp3")                                 = "mp3";
     * getHrefInnerHtml("<a innerHtml</a>")                    = "<a innerHtml</a>";
     * getHrefInnerHtml("<a>innerHtml</a>")                    = "innerHtml";
     * getHrefInnerHtml("<a<a>innerHtml</a>")                    = "innerHtml";
     * getHrefInnerHtml("<a href="baidu.com">innerHtml</a>")               = "innerHtml";
     * getHrefInnerHtml("<a href="baidu.com" title="baidu">innerHtml</a>") = "innerHtml";
     * getHrefInnerHtml("   <a>innerHtml</a>  ")                           = "innerHtml";
     * getHrefInnerHtml("<a>innerHtml</a></a>")                      = "innerHtml";
     * getHrefInnerHtml("jack<a>innerHtml</a></a>")                  = "innerHtml";
     * getHrefInnerHtml("<a>innerHtml1</a><a>innerHtml2</a>")        = "innerHtml2";
     * 
     *
     * @param href
     * @return 
 

  
     * 
  
if href is null, return ""
     * 
  
if not match regx, return source
     * 
  
return the last string that match regx
     * 
 
     */
    public static String getHrefInnerHtml(String href) {
        if (isEmpty(href)) {
            return "";
        }

        String hrefReg = ".*<[\\s]*a[\\s]*.*>(.+?)<[\\s]*/a[\\s]*>.*";
        Pattern hrefPattern = Pattern.compile(hrefReg, Pattern.CASE_INSENSITIVE);
        Matcher hrefMatcher = hrefPattern.matcher(href);
        if (hrefMatcher.matches()) {
            return hrefMatcher.group(1);
        }
        return href;
    }

    /**
     * process special char in html
     * 

     * 
     * htmlEscapeCharsToString(null) = null;
     * htmlEscapeCharsToString("") = "";
     * htmlEscapeCharsToString("mp3") = "mp3";
     * htmlEscapeCharsToString("mp3<") = "mp3<";
     * htmlEscapeCharsToString("mp3>") = "mp3\>";
     * htmlEscapeCharsToString("mp3&mp4") = "mp3&mp4";
     * htmlEscapeCharsToString("mp3"mp4") = "mp3\"mp4";
     * htmlEscapeCharsToString("mp3<>&"mp4") = "mp3\<\>&\"mp4";
     * 
     *
     * @param source
     * @return
     */
    public static String htmlEscapeCharsToString(String source) {
        return StringUtils.isEmpty(source) ? source : source.replaceAll("<", "<").replaceAll(">", ">")
                .replaceAll("&", "&").replaceAll(""", "\"");
    }

    /**
     * transform half width char to full width char
     * 

     * 
     * fullWidthToHalfWidth(null) = null;
     * fullWidthToHalfWidth("") = "";
     * fullWidthToHalfWidth(new String(new char[] {12288})) = " ";
     * fullWidthToHalfWidth("！＂＃＄％＆) = "!\"#$%&";
     * 
     *
     * @param s
     * @return
     */
    public static String fullWidthToHalfWidth(String s) {
        if (isEmpty(s)) {
            return s;
        }

        char[] source = s.toCharArray();
        for (int i = 0; i < source.length; i++) {
            if (source[i] == 12288) {
                source[i] = ' ';
                // } else if (source[i] == 12290) {
                // source[i] = '.';
            } else if (source[i] >= 65281 && source[i] <= 65374) {
                source[i] = (char) (source[i] - 65248);
            } else {
                source[i] = source[i];
            }
        }
        return new String(source);
    }

    /**
     * transform full width char to half width char
     * 

     * 
     * halfWidthToFullWidth(null) = null;
     * halfWidthToFullWidth("") = "";
     * halfWidthToFullWidth(" ") = new String(new char[] {12288});
     * halfWidthToFullWidth("!\"#$%&) = "！＂＃＄％＆";
     * 
     *
     * @param s
     * @return
     */
    public static String halfWidthToFullWidth(String s) {
        if (isEmpty(s)) {
            return s;
        }

        char[] source = s.toCharArray();
        for (int i = 0; i < source.length; i++) {
            if (source[i] == ' ') {
                source[i] = (char) 12288;
                // } else if (source[i] == '.') {
                // source[i] = (char)12290;
            } else if (source[i] >= 33 && source[i] <= 126) {
                source[i] = (char) (source[i] + 65248);
            } else {
                source[i] = source[i];
            }
        }
        return new String(source);
    }

}