stringutils.java

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     * StringUtils.stripStart("abc", null)      = "abc"
     * StringUtils.stripStart("  abc", null)    = "abc"
     * StringUtils.stripStart("abc  ", null)    = "abc  "
     * StringUtils.stripStart(" abc ", null)    = "abc "
     * StringUtils.stripStart("yxabc  ", "xyz") = "abc  "
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, <code>null</code> if null String input
     */
    public static String stripStart(String str, String stripChars) {
        int start = getStripStart(str, stripChars);
        return (start <= 0) ? str : str.substring(start);
    }

    private static int getStripStart(String str, String stripChars) {
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return -1;
        }
        int start = 0;
        if (stripChars == null) {
            while ((start != strLen) && Character.isWhitespace(str.charAt(start))) {
                start++;
            }
        } else if (stripChars.length() == 0) {
            return start;
        } else {
            while ((start != strLen) && (stripChars.indexOf(str.charAt(start)) != -1)) {
                start++;
            }
        }
        return start;
    }

    /**
     * <p>Strips any of a set of characters from the end of a String.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is <code>null</code>, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * StringUtils.stripEnd(null, *)          = null
     * StringUtils.stripEnd("", *)            = ""
     * StringUtils.stripEnd("abc", "")        = "abc"
     * StringUtils.stripEnd("abc", null)      = "abc"
     * StringUtils.stripEnd("  abc", null)    = "  abc"
     * StringUtils.stripEnd("abc  ", null)    = "abc"
     * StringUtils.stripEnd(" abc ", null)    = " abc"
     * StringUtils.stripEnd("  abcyx", "xyz") = "  abc"
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, <code>null</code> if null String input
     */
    public static String stripEnd(String str, String stripChars) {
        int end = getStripEnd(str, stripChars);
        return (end < 0) ? str : str.substring(0, end);
    }

    private static int getStripEnd(String str, String stripChars) {
        int end;
        if (str == null || (end = str.length()) == 0) {
            return -1;
        }
        if (stripChars == null) {
            while ((end != 0) && Character.isWhitespace(str.charAt(end - 1))) {
                end--;
            }
        } else if (stripChars.length() == 0) {
            return end;
        } else {
            while ((end != 0) && (stripChars.indexOf(str.charAt(end - 1)) != -1)) {
                end--;
            }
        }
        return end;
    }

    /**
     * write the escaped version of a given string
     * 
     * @param str string to be encoded
     * @return a new escaped <code>String</code>, <code>null</code> if null string input
     */
    public static String escapeNumericChar(String str) {
        if (str == null) {
            return null;
        }
        try {
            StringWriter writer = new StringWriter(str.length());
            escapeNumericChar(writer, str);
            return writer.toString();
        } catch (IOException ioe) {
            // this should never ever happen while writing to a StringWriter
            ioe.printStackTrace();
            return null;
        }
    }

    /**
     * write the escaped version of a given string
     * 
     * @param out       writer to write this string to
     * @param str       string to be encoded
     */
    public static void escapeNumericChar(Writer out, String str)
            throws IOException {
        if (str == null) {
            return;
        }
        int length = str.length();
        char character;
        for (int i = 0; i < length; i++) {
            character = str.charAt( i );
            if (character > 0x7F) {
                out.write("&#x");
                out.write(Integer.toHexString(character).toUpperCase());
                out.write(";");
            } else {
                out.write(character);
            }
        }
    }

    /**
     * <p>Unescapes numeric character referencs found in the <code>String</code>.</p>
     *
     * <p>For example, it will return a unicode string which means the specified numeric
     *    character references looks like "&#x3088;&#x3046;&#x3053;&#x305d;".</p>
     * 
     * @param str  the <code>String</code> to unescape, may be null
     * @return a new unescaped <code>String</code>, <code>null</code> if null string input
     */
    public static String unescapeNumericChar(String str) {
        if (str == null) {
            return null;
        }
        try {
            StringWriter writer = new StringWriter(str.length());
            unescapeNumericChar(writer, str);
            return writer.toString();
        } catch (IOException ioe) {
            // this should never ever happen while writing to a StringWriter
            ioe.printStackTrace();
            return null;
        }
    }

    /**
     * <p>Unescapes numeric character references found in the <code>String</code> to a
     * <code>Writer</code>.</p>
     *
     * <p>For example, it will return a unicode string which means the specified numeric
     *    character references looks like "&#x3088;&#x3046;&#x3053;&#x305d;".</p>
     * 
     * <p>A <code>null</code> string input has no effect.</p>
     * 
     * @param out  the <code>Writer</code> used to output unescaped characters
     * @param str  the <code>String</code> to unescape, may be null
     * @throws IllegalArgumentException if the Writer is <code>null</code>
     * @throws java.io.IOException if error occurs on underlying Writer
     */
    public static void unescapeNumericChar(Writer out, String str) throws IOException {
        if (out == null) {
            throw new IllegalArgumentException("The Writer must not be null");
        }
        if (str == null) {
            return;
        }

        int sz = str.length();
        StringBuffer unicode = new StringBuffer(4);
        StringBuffer escapes = new StringBuffer(3);
        boolean inUnicode = false;

        for (int i = 0; i < sz; i++) {
            char ch = str.charAt(i);
            if (inUnicode) {
                // if in unicode, then we're reading unicode
                // values in somehow
                unicode.append(ch);
                if (unicode.length() == 4) {
                    // unicode now contains the four hex digits
                    // which represents our unicode character
                    try {
                        int value = Integer.parseInt(unicode.toString(), 16);
                        out.write((char) value);
                        unicode.setLength(0);
                        // need to skip the delimiter - ';'
                        i = i + 1;
                        inUnicode = false;
                    } catch (NumberFormatException nfe) {
                        throw new InternalException(nfe);
                    }
                }
                continue;
            } else if (ch=='&') {
                // Start of the escape sequence ...
                // At least, the numeric character references require 8 bytes to
                // describe a Unicode character like as"&#xFFFF;"
                if (i+7 <= sz) {
                    escapes.append(ch);
                    escapes.append(str.charAt(i+1));
                    escapes.append(str.charAt(i+2));
                    if (escapes.toString().equals("&#x") && str.charAt(i+7)==';') {
                        inUnicode = true;
                    } else {
                        out.write(escapes.toString());
                    }
                    escapes.setLength(0);
                    // need to skip the escaping chars - '&#x'
                    i = i + 2;
                } else {
                    out.write(ch);
                }
                continue;
            }
            out.write(ch);
        }
    }
}