stringutils.java

这个是网络上下载的一个struct框架的程序

     */
    public synchronized static final String hash(String data) {
        if (digest == null) {
            try {
                digest = MessageDigest.getInstance("MD5");
            }
            catch (NoSuchAlgorithmException nsae) {
               
            }
        }
        // Now, compute hash.
        try {
            digest.update(data.getBytes("utf-8"));
        }
        catch (UnsupportedEncodingException e) {
            
        }
        return encodeHex(digest.digest());
    }

    /**
     * Turns an array of bytes into a String representing each byte as an
     * unsigned hex number.
     * <p>
     * Method by Santeri Paavolainen, Helsinki Finland 1996<br>
     * (c) Santeri Paavolainen, Helsinki Finland 1996<br>
     * Distributed under LGPL.
     *
     * @param bytes an array of bytes to convert to a hex-string
     * @return generated hex string
     */
    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 a hex encoded String to transform into a byte array.
     * @return a byte array representing the hex String[
     */
    public static final 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) {
            int newByte = 0x00;
            newByte |= hexCharToByte(chars[i]);
            newByte <<= 4;
            newByte |= hexCharToByte(chars[i+1]);
            bytes[byteCount] = (byte)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.
    //*
    //*     Copyright (c) 1999, Bob Withers - [e-mail]
    //*
    //* This code may be freely used for any purpose, either personal
    //* or commercial, provided the authors copyright notice remains
    //* intact.
    //*********************************************************************

    /**
     * Encodes a String as a base64 String.
     *
     * @param data a String to encode.
     * @return a base64 encoded String.
     */
    public static String encodeBase64(String data) {
        byte [] bytes = null;
        try {
            bytes = data.getBytes("ISO-8859-1");
        }
        catch (UnsupportedEncodingException uee) {
            //Log.error(uee);
        }
        return encodeBase64(bytes);
    }

    /**
     * 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) {
        byte [] bytes = null;
        try {
            bytes = data.getBytes("ISO-8859-1");
        }
        catch (UnsupportedEncodingException uee) {
            //Log.error(uee);
        }
        return decodeBase64(bytes);
    }

    /**
     * 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(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(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(). <p>
     *
     * 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();
            // Remove characters that are not needed.
            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.<p>
     *
     * The specified length must be at least one. If not, the method will return
     * null.
     *
     * @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;
        }
        // Create a char buffer to put random letters and numbers in.
        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, -1) 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 the index in <code>string</code> to start looking for a
    *       whitespace boundary at.
    * @param minLength the minimum length the word should be chopped at. This is helpful
    *       for words with no natural boundaries, ie: "thisisareallylonglonglongword".