Java实现的文本字符串操作工具类实例【数据替换，加密解密操作】

package com.gcloud.common;
import org.apache.commons.lang.StringUtils;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.text.BreakIterator;
import java.util.ArrayList;
import java.util.Date;
import java.util.Random;
/**
 * 文本字符串工具类
 * Created by charlin on 2017/9/10.
 */
public class TextUtil {
  private static final char[] QUOTE_ENCODE = """.toCharArray();
  private static final char[] AMP_ENCODE = "&".toCharArray();
  private static final char[] LT_ENCODE = "<".toCharArray();
  private static final char[] GT_ENCODE = ">".toCharArray();
  private final static String[] hex = { "00", "01", "02", "03", "04", "05",
      "06", "07", "08", "09", "0A", "0B", "0C", "0D", "0E", "0F", "10",
      "11", "12", "13", "14", "15", "16", "17", "18", "19", "1A", "1B",
      "1C", "1D", "1E", "1F", "20", "21", "22", "23", "24", "25", "26",
      "27", "28", "29", "2A", "2B", "2C", "2D", "2E", "2F", "30", "31",
      "32", "33", "34", "35", "36", "37", "38", "39", "3A", "3B", "3C",
      "3D", "3E", "3F", "40", "41", "42", "43", "44", "45", "46", "47",
      "48", "49", "4A", "4B", "4C", "4D", "4E", "4F", "50", "51", "52",
      "53", "54", "55", "56", "57", "58", "59", "5A", "5B", "5C", "5D",
      "5E", "5F", "60", "61", "62", "63", "64", "65", "66", "67", "68",
      "69", "6A", "6B", "6C", "6D", "6E", "6F", "70", "71", "72", "73",
      "74", "75", "76", "77", "78", "79", "7A", "7B", "7C", "7D", "7E",
      "7F", "80", "81", "82", "83", "84", "85", "86", "87", "88", "89",
      "8A", "8B", "8C", "8D", "8E", "8F", "90", "91", "92", "93", "94",
      "95", "96", "97", "98", "99", "9A", "9B", "9C", "9D", "9E", "9F",
      "A0", "A1", "A2", "A3", "A4", "A5", "A6", "A7", "A8", "A9", "AA",
      "AB", "AC", "AD", "AE", "AF", "B0", "B1", "B2", "B3", "B4", "B5",
      "B6", "B7", "B8", "B9", "BA", "BB", "BC", "BD", "BE", "BF", "C0",
      "C1", "C2", "C3", "C4", "C5", "C6", "C7", "C8", "C9", "CA", "CB",
      "CC", "CD", "CE", "CF", "D0", "D1", "D2", "D3", "D4", "D5", "D6",
      "D7", "D8", "D9", "DA", "DB", "DC", "DD", "DE", "DF", "E0", "E1",
      "E2", "E3", "E4", "E5", "E6", "E7", "E8", "E9", "EA", "EB", "EC",
      "ED", "EE", "EF", "F0", "F1", "F2", "F3", "F4", "F5", "F6", "F7",
      "F8", "F9", "FA", "FB", "FC", "FD", "FE", "FF" };
  private final static byte[] val = { 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x00, 0x01,
      0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08, 0x09, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x0A, 0x0B, 0x0C, 0x0D, 0x0E, 0x0F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F,
      0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F, 0x3F };
  private static MessageDigest digest = null;
  /**
   * 替换字符串
   * @param line
   * @param oldStr
   * @param newStr
   * @return
   */
  public static String replace(String line , String oldStr, String newStr){
    if (StringUtils.isEmpty(line)) return null;
    int index = 0;
    if ((index = line.indexOf(oldStr, index)) >= 0){
      char[] charArray = line.toCharArray();
      char[] newStrArray = newStr.toCharArray();
      int oldLen = oldStr.length();
      StringBuffer buf = new StringBuffer(charArray.length);
      buf.append(charArray, 0, index).append(newStrArray);
      index += oldLen;
      int i = index;
      while((index = line.indexOf(oldStr, index)) > 0){
        buf.append(charArray, i, index - i).append(newStrArray);
        index += oldLen;
        i = index;
      }
      buf.append(charArray, i, charArray.length - i);
      return buf.toString();
    }
    return line;
  }
  /**
   * 替换字符串,并存入替换次数
   * @param line
   * @param oldStr
   * @param newStr
   * @return
   */
  public static String replace(String line , String oldStr, String newStr, int[] countArr){
    if (StringUtils.isEmpty(line)) return null;
    int index = 0;
    if ((index = line.indexOf(oldStr, index)) >= 0){
      int count = 0;
      count++;
      char[] charArray = line.toCharArray();
      char[] newStrArray = newStr.toCharArray();
      int oldLen = oldStr.length();
      StringBuffer buf = new StringBuffer(charArray.length);
      buf.append(charArray, 0, index).append(newStrArray);
      index += oldLen;
      int i = index;
      while((index = line.indexOf(oldStr, index)) > 0){
        buf.append(charArray, i, index - i).append(newStrArray);
        index += oldLen;
        i = index;
        count++;
      }
      buf.append(charArray, i, charArray.length - i);
      countArr[0] = count;
      return buf.toString();
    }
    return line;
  }
  /**
   * 替换字符串，不区分大小写
   * @param line
   * @param oldStr
   * @param newStr
   * @return
   */
  public static String replaceIgnoreCase(String line , String oldStr, String newStr){
    if (StringUtils.isEmpty(line)) return null;
    int index = 0;
    line = line.toLowerCase();
    oldStr = oldStr.toLowerCase();
    if ((index = line.indexOf(oldStr, index)) >= 0){
      char[] charArray = line.toCharArray();
      char[] newStrArray = newStr.toCharArray();
      int oldLen = oldStr.length();
      StringBuffer buf = new StringBuffer(charArray.length);
      buf.append(charArray, 0, index).append(newStrArray);
      index += oldLen;
      int i = index;
      while((index = line.indexOf(oldStr, index)) > 0){
        buf.append(charArray, i, index - i).append(newStrArray);
        index += oldLen;
        i = index;
      }
      buf.append(charArray, i, charArray.length - i);
      return buf.toString();
    }
    return line;
  }
  /**
   * 替换字符串，不区分大小写, 并存入替换次数
   * @param line
   * @param oldStr
   * @param newStr
   * @return
   */
  public static String replaceIgnoreCase(String line , String oldStr, String newStr, int[] countArr){
    if (StringUtils.isEmpty(line)) return null;
    int index = 0;
    line = line.toLowerCase();
    oldStr = oldStr.toLowerCase();
    if ((index = line.indexOf(oldStr, index)) >= 0){
      char[] charArray = line.toCharArray();
      char[] newStrArray = newStr.toCharArray();
      int oldLen = oldStr.length();
      StringBuffer buf = new StringBuffer(charArray.length);
      buf.append(charArray, 0, index).append(newStrArray);
      index += oldLen;
      int i = index;
      int count = 0;
      while((index = line.indexOf(oldStr, index)) > 0){
        count ++;
        buf.append(charArray, i, index - i).append(newStrArray);
        index += oldLen;
        i = index;
      }
      buf.append(charArray, i, charArray.length - i);
      countArr[0] = count;
      return buf.toString();
    }
    return line;
  }
  /**
   * 替换页面html标签
   * @param htmlStr
   * @return
   */
  public static String escapeHTMLTags(String htmlStr) {
    if (StringUtils.isEmpty(htmlStr)) return null;
    char ch;
    int last = 0;
    char[] htmlStrArr = htmlStr.toCharArray();
    int len = htmlStrArr.length;
    StringBuffer outBuf = new StringBuffer((int) (len * 1.3));
    int i = 0;
    for (; i < len; i++) {
      ch = htmlStrArr[i];
      if (ch > '>') {
        continue;
      } else if (ch == '<') {
        if (i > last) {
          outBuf.append(htmlStrArr, last, i - last);
        }
        last = i + 1;
        outBuf.append(LT_ENCODE);
      } else if (ch == '>') {
        if (i > last) {
          outBuf.append(htmlStrArr, last, i - last);
        }
        last = i + 1;
        outBuf.append(GT_ENCODE);
      }
    }
    if (last == 0) {
      return htmlStr;
    }
    if (i > last) {
      outBuf.append(htmlStrArr, last, i - last);
    }
    return outBuf.toString();
  }
  /**
   * Hashes a String using the Md5 algorithm and returns the result as a
   * String of hexadecimal numbers. This method is synchronized to avoid
   * excessive MessageDigest object creation. If calling this method becomes a
   * bottleneck in your code, you may wish to maintain a pool of MessageDigest
   * objects instead of using this method.
   * @param data
   * @return
   */
  public synchronized static String hash(String data) {
    if (digest == null) {
      try {
        digest = MessageDigest.getInstance("MD5");
      } catch (NoSuchAlgorithmException e) {
        System.err.println("Failed to load the MD5 MessageDigest.Jive will be unable to function normally.");
        e.printStackTrace();
      }
    }
    digest.update(data.getBytes());
    return encodeHex(digest.digest());
  }
  /**
   * Turns an array of bytes into a String representing each byte as an
   * unsigned hex number.
   * @param bytes
   * @return
   */
  public static final String encodeHex(byte[] bytes) {
    StringBuffer buf = new StringBuffer(bytes.length * 2);
    int i;
    for (i = 0; i < bytes.length; i++) {
      if (((int) bytes[i] & 0xff) < 0x10) {
        buf.append("0");
      }
      buf.append(Long.toString((int) bytes[i] & 0xff, 16));
    }
    return buf.toString();
  }
  /**
   * Turns a hex encoded string into a byte array. It is specifically meant to
   * "reverse" the toHex(byte[]) method.
   * @param hex
   * @return
   */
  public static byte[] decodeHex(String hex) {
    char[] chars = hex.toCharArray();
    byte[] bytes = new byte[chars.length / 2];
    int byteCount = 0;
    for (int i = 0; i < chars.length; i += 2) {
      byte newByte = 0x00;
      newByte |= hexCharToByte(chars[i]);
      newByte <<= 4;
      newByte |= hexCharToByte(chars[i + 1]);
      bytes[byteCount] = newByte;
      byteCount++;
    }
    return bytes;
  }
  /**
   * Returns the the byte value of a hexadecmical char (0-f). It's assumed
   * that the hexidecimal chars are lower case as appropriate.
   * @param ch a hexedicmal character (0-f)
   * @return  the byte value of the character (0x00-0x0F)
   */
  private static final byte hexCharToByte(char ch) {
    switch (ch) {
      case '0':
        return 0x00;
      case '1':
        return 0x01;
      case '2':
        return 0x02;
      case '3':
        return 0x03;
      case '4':
        return 0x04;
      case '5':
        return 0x05;
      case '6':
        return 0x06;
      case '7':
        return 0x07;
      case '8':
        return 0x08;
      case '9':
        return 0x09;
      case 'a':
        return 0x0A;
      case 'b':
        return 0x0B;
      case 'c':
        return 0x0C;
      case 'd':
        return 0x0D;
      case 'e':
        return 0x0E;
      case 'f':
        return 0x0F;
    }
    return 0x00;
  }
  // *********************************************************************
  // * Base64 - a simple base64 encoder and decoder.
  // *********************************************************************
  /**
   * Encodes a String as a base64 String.
   * @param data a String to encode.
   * @return a base64 encoded String.
   */
  public static String encodeBase64(String data) {
    return encodeBase64(data.getBytes());
  }
  /**
   * Encodes a byte array into a base64 String.
   * @param data a byte array to encode.
   * @return a base64 encode String.
   */
  public static String encodeBase64(byte[] data) {
    int c;
    int len = data.length;
    StringBuffer ret = new StringBuffer(((len / 3) + 1) * 4);
    for (int i = 0; i < len; ++i) {
      c = (data[i] >> 2) & 0x3f;
      ret.append(cvt.charAt(c));
      c = (data[i] << 4) & 0x3f;
      if (++i < len)
        c |= (data[i] >> 4) & 0x0f;
      ret.append(cvt.charAt(c));
      if (i < len) {
        c = (data[i] << 2) & 0x3f;
        if (++i < len)
          c |= (data[i] >> 6) & 0x03;
        ret.append(cvt.charAt(c));
      } else {
        ++i;
        ret.append((char) fillchar);
      }
      if (i < len) {
        c = data[i] & 0x3f;
        ret.append(cvt.charAt(c));
      } else {
        ret.append((char) fillchar);
      }
    }
    return ret.toString();
  }
  /**
   * Decodes a base64 String.
   * @param data a base64 encoded String to decode.
   * @return the decoded String.
   */
  public static String decodeBase64(String data) {
    return decodeBase64(data.getBytes());
  }
  /**
   * Decodes a base64 aray of bytes.
   * @param data a base64 encode byte array to decode.
   * @return the decoded String.
   */
  public static String decodeBase64(byte[] data) {
    int c, c1;
    int len = data.length;
    StringBuffer ret = new StringBuffer((len * 3) / 4);
    for (int i = 0; i < len; ++i) {
      c = cvt.indexOf(data[i]);
      ++i;
      c1 = cvt.indexOf(data[i]);
      c = ((c << 2) | ((c1 >> 4) & 0x3));
      ret.append((char) c);
      if (++i < len) {
        c = data[i];
        if (fillchar == c)
          break;
        c = cvt.indexOf((char) c);
        c1 = ((c1 << 4) & 0xf0) | ((c >> 2) & 0xf);
        ret.append((char) c1);
      }
      if (++i < len) {
        c1 = data[i];
        if (fillchar == c1)
          break;
        c1 = cvt.indexOf((char) c1);
        c = ((c << 6) & 0xc0) | c1;
        ret.append((char) c);
      }
    }
    return ret.toString();
  }
  private static final int fillchar = '=';
  private static final String cvt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" + "abcdefghijklmnopqrstuvwxyz" + "0123456789+/";
  /**
   * Converts a line of text into an array of lower case words using a
   * BreakIterator.wordInstance().
   * This method is under the Jive Open Source Software License and was
   * written by Mark Imbriaco.
   * @param text a String of text to convert into an array of words
   * @return text broken up into an array of words.
   */
  public static final String[] toLowerCaseWordArray(String text) {
    if (text == null || text.length() == 0) {
      return new String[0];
    }
    ArrayList wordList = new ArrayList();
    BreakIterator boundary = BreakIterator.getWordInstance();
    boundary.setText(text);
    int start = 0;
    for (int end = boundary.next(); end != BreakIterator.DONE; start = end, end = boundary.next()) {
      String tmp = text.substring(start, end).trim();
      tmp = replace(tmp, "+", "");
      tmp = replace(tmp, "/", "");
      tmp = replace(tmp, "\\", "");
      tmp = replace(tmp, "#", "");
      tmp = replace(tmp, "*", "");
      tmp = replace(tmp, ")", "");
      tmp = replace(tmp, "(", "");
      tmp = replace(tmp, "&", "");
      if (tmp.length() > 0) {
        wordList.add(tmp);
      }
    }
    return (String[]) wordList.toArray(new String[wordList.size()]);
  }
  /**
   * Pseudo-random number generator object for use with randomString(). The
   * Random class is not considered to be cryptographically secure, so only
   * use these random Strings for low to medium security applications.
   */
  private static Random randGen = new Random();
  /**
   * Array of numbers and letters of mixed case. Numbers appear in the list
   * twice so that there is a more equal chance that a number will be picked.
   * We can use the array to get a random number or letter by picking a random
   * array index.
   */
  private static char[] numbersAndLetters = ("0123456789abcdefghijklmnopqrstuvwxyz" + "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ").toCharArray();
  /**
   * Returns a random String of numbers and letters (lower and upper case) of
   * the specified length. The method uses the Random class that is built-in
   * to Java which is suitable for low to medium grade security uses. This
   * means that the output is only pseudo random, i.e., each number is
   * mathematically generated so is not truly random.
   * @param length the desired length of the random String to return.
   * @return a random String of numbers and letters of the specified length.
   */
  public static final String randomString(int length) {
    if (length < 1) {
      return null;
    }
    char[] randBuffer = new char[length];
    for (int i = 0; i < randBuffer.length; i++) {
      randBuffer[i] = numbersAndLetters[randGen.nextInt(71)];
    }
    return new String(randBuffer);
  }
  /**
   * Intelligently chops a String at a word boundary (whitespace) that occurs
   * at the specified index in the argument or before. However, if there is a
   * newline character before <code>length</code>, the String will be
   * chopped there. If no newline or whitespace is found in
   * <code>string</code> up to the index <code>length</code>, the String
   * will chopped at <code>length</code>.
   * <p>
   * For example, chopAtWord("This is a nice String", 10) will return "This is
   * a" which is the first word boundary less than or equal to 10 characters
   * into the original String.
   * @param string the String to chop.
   * @param length
   * @return a substring of <code>string</code> whose length is less than or
   *     equal to <code>length</code>, and that is chopped at
   *     whitespace.
   */
  public static final String chopAtWord(String string, int length) {
    if (string == null) {
      return string;
    }
    char[] charArray = string.toCharArray();
    int sLength = string.length();
    if (length < sLength) {
      sLength = length;
    }
    // First check if there is a newline character before length; if so,
    // chop word there.
    for (int i = 0; i < sLength - 1; i++) {
      // Windows
      if (charArray[i] == '\r' && charArray[i + 1] == '\n') {
        return string.substring(0, i + 1);
      }
      // Unix
      else if (charArray[i] == '\n') {
        return string.substring(0, i);
      }
    }
    // Also check boundary case of Unix newline
    if (charArray[sLength - 1] == '\n') {
      return string.substring(0, sLength - 1);
    }
    // Done checking for newline, now see if the total string is less than
    // the specified chop point.
    if (string.length() < length) {
      return string;
    }
    // No newline, so chop at the first whitespace.
    for (int i = length - 1; i > 0; i--) {
      if (charArray[i] == ' ') {
        return string.substring(0, i).trim();
      }
    }
    // Did not find word boundary so return original String chopped at
    // specified length.
    return string.substring(0, length);
  }
  /**
   * Escapes all necessary characters in the String so that it can be used in
   * an XML doc.
   * @param string the string to escape.
   * @return the string with appropriate characters escaped.
   */
  public static final String escapeForXML(String string) {
    if (string == null) {
      return null;
    }
    char ch;
    int i = 0;
    int last = 0;
    char[] input = string.toCharArray();
    int len = input.length;
    StringBuffer out = new StringBuffer((int) (len * 1.3));
    for (; i < len; i++) {
      ch = input[i];
      if (ch > '>') {
        continue;
      } else if (ch == '<') {
        if (i > last) {
          out.append(input, last, i - last);
        }
        last = i + 1;
        out.append(LT_ENCODE);
      } else if (ch == '&') {
        if (i > last) {
          out.append(input, last, i - last);
        }
        last = i + 1;
        out.append(AMP_ENCODE);
      } else if (ch == '"') {
        if (i > last) {
          out.append(input, last, i - last);
        }
        last = i + 1;
        out.append(QUOTE_ENCODE);
      }
    }
    if (last == 0) {
      return string;
    }
    if (i > last) {
      out.append(input, last, i - last);
    }
    return out.toString();
  }
  /**
   * Unescapes the String by converting XML escape sequences back into normal
   * characters.
   * @param string the string to unescape.
   * @return the string with appropriate characters unescaped.
   */
  public static final String unescapeFromXML(String string) {
    string = replace(string, "&lt;", "<");
    string = replace(string, "&gt;", ">");
    string = replace(string, "&quot;", "\"");
    return replace(string, "&amp;", "&");
  }
  public static String escape(String s) {
    StringBuffer sbuf = new StringBuffer();
    int len = s.length();
    for (int i = 0; i < len; i++) {
      int ch = s.charAt(i);
      if (ch == ' ') { // space : map to '+'
        sbuf.append('+');
      } else if ('A' <= ch && ch <= 'Z') { // 'A'..'Z' : as it was
        sbuf.append((char) ch);
      } else if ('a' <= ch && ch <= 'z') { // 'a'..'z' : as it was
        sbuf.append((char) ch);
      } else if ('0' <= ch && ch <= '9') { // '0'..'9' : as it was
        sbuf.append((char) ch);
      } else if (ch == '-'
          || ch == '_' // unreserved : as it was
          || ch == '.' || ch == '!' || ch == '~' || ch == '*'
          || ch == '\'' || ch == '(' || ch == ')') {
        sbuf.append((char) ch);
      } else if (ch <= 0x007F) { // other ASCII : map to %XX
        sbuf.append('%');
        sbuf.append(hex[ch]);
      } else { // unicode : map to %uXXXX
        sbuf.append('%');
        sbuf.append('u');
        sbuf.append(hex[(ch >>> 8)]);
        sbuf.append(hex[(0x00FF & ch)]);
      }
    }
    return sbuf.toString();
  }
  public static String unescape(String s) {
    StringBuffer sbuf = new StringBuffer();
    int i = 0;
    int len = s.length();
    while (i < len) {
      int ch = s.charAt(i);
      if (ch == '+') { // + : map to ' '
        sbuf.append(' ');
      } else if ('A' <= ch && ch <= 'Z') { // 'A'..'Z' : as it was
        sbuf.append((char) ch);
      } else if ('a' <= ch && ch <= 'z') { // 'a'..'z' : as it was
        sbuf.append((char) ch);
      } else if ('0' <= ch && ch <= '9') { // '0'..'9' : as it was
        sbuf.append((char) ch);
      } else if (ch == '-'
          || ch == '_' // unreserved : as it was
          || ch == '.' || ch == '!' || ch == '~' || ch == '*'
          || ch == '\'' || ch == '(' || ch == ')') {
        sbuf.append((char) ch);
      } else if (ch == '%') {
        int cint = 0;
        if ('u' != s.charAt(i + 1)) { // %XX : map to ascii(XX)
          cint = (cint << 4) | val[s.charAt(i + 1)];
          cint = (cint << 4) | val[s.charAt(i + 2)];
          i += 2;
        } else { // %uXXXX : map to unicode(XXXX)
          cint = (cint << 4) | val[s.charAt(i + 2)];
          cint = (cint << 4) | val[s.charAt(i + 3)];
          cint = (cint << 4) | val[s.charAt(i + 4)];
          cint = (cint << 4) | val[s.charAt(i + 5)];
          i += 5;
        }
        sbuf.append((char) cint);
      }
      i++;
    }
    return sbuf.toString();
  }
  private static final char[] zeroArray = "0000000000000000".toCharArray();
  /**
   * Pads the supplied String with 0's to the specified length and returns the
   * result as a new String. For example, if the initial String is "9999" and
   * the desired length is 8, the result would be "00009999". This type of
   * padding is useful for creating numerical values that need to be stored
   * and sorted as character data. Note: the current implementation of this
   * method allows for a maximum <tt>length</tt> of 16.
   *
   * @param string
   *      the original String to pad.
   * @param length
   *      the desired length of the new padded String.
   * @return a new String padded with the required number of 0's.
   */
  public static final String zeroPadString(String string, int length) {
    if (string == null || string.length() > length) {
      return string;
    }
    StringBuffer buf = new StringBuffer(length);
    buf.append(zeroArray, 0, length - string.length()).append(string);
    return buf.toString();
  }
  /**
   * Formats a Date as a fifteen character long String made up of the Date's
   * padded millisecond value.
   * @return a Date encoded as a String.
   */
  public static final String dateToMillis(Date date) {
    return zeroPadString(Long.toString(date.getTime()), 15);
  }
  public static void main(String[] args) {
    System.out.println(replace("aaaaabbbcccc", "aa", "gg"));
    System.out.println(replaceIgnoreCase("AAAAbbbcccc", "aa", "gg"));
    System.out.println(escapeHTMLTags("AAAAbb<bcccc>"));
  }
}