java汉字及unicode互转

java 汉字和unicode互转

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import java.io.UnsupportedEncodingException;
public class UnicodeConverter {
    public static void main(String[] args) throws UnsupportedEncodingException {
        String s = " \t小\u51AC";
        System.out.println("Original:\t\t" + s);
        s = toEncodedUnicode(s, true);
        System.out.println("to unicode:\t\t" + s);
        s = fromEncodedUnicode(s.toCharArray(), 0, s.length());
        System.out.println("from unicode:\t" + s);
    }
    private static final char[] hexDigit = {
        '0',
        '1',
        '2',
        '3',
        '4',
        '5',
        '6',
        '7',
        '8',
        '9',
        'A',
        'B',
        'C',
        'D',
        'E',
        'F'
    };
    private static char toHex(int nibble) {
        return hexDigit[(nibble & 0xF)];
    }
    /**
     * 将字符串编码成 Unicode 形式的字符串. 如 "小" to "\u5c0f"
     * Converts unicodes to encoded \\uxxxx and escapes
     * special characters with a preceding slash
     * 
     * @param theString
     *        待转换成Unicode编码的字符串。
     * @param escapeSpace
     *        是否忽略空格,为true时在空格后面是否加个反斜杠。
     * @return 返回转换后Unicode编码的字符串。
     */
    public static String toEncodedUnicode(String theString, boolean escapeSpace) {
        int len = theString.length();
        int bufLen = len * 2;
        if (bufLen < 0) {
            bufLen = Integer.MAX_VALUE;
        }
        StringBuffer outBuffer = new StringBuffer(bufLen);
        for (int x = 0; x < len; x++) {
            char aChar = theString.charAt(x);
            // Handle common case first, selecting largest block that
            // avoids the specials below
            if ((aChar > 61) && (aChar < 127)) {
                if (aChar == '\\') {
                    outBuffer.append('\\');
                    outBuffer.append('\\');
                    continue;
                }
                outBuffer.append(aChar);
                continue;
            }
            switch (aChar) {
                case ' ':
                    if (x == 0 || escapeSpace) outBuffer.append('\\');
                    outBuffer.append(' ');
                    break;
                case '\t':
                    outBuffer.append('\\');
                    outBuffer.append('t');
                    break;
                case '\n':
                    outBuffer.append('\\');
                    outBuffer.append('n');
                    break;
                case '\r':
                    outBuffer.append('\\');
                    outBuffer.append('r');
                    break;
                case '\f':
                    outBuffer.append('\\');
                    outBuffer.append('f');
                    break;
                case '=': // Fall through
                case ':': // Fall through
                case '#': // Fall through
                case '!':
                    outBuffer.append('\\');
                    outBuffer.append(aChar);
                    break;
                default:
                    if ((aChar < 0x0020) || (aChar > 0x007e)) {
                        // 每个unicode有16位,每四位对应的16进制从高位保存到低位
                        outBuffer.append('\\');
                        outBuffer.append('u');
                        outBuffer.append(toHex((aChar >> 12) & 0xF));
                        outBuffer.append(toHex((aChar >> 8) & 0xF));
                        outBuffer.append(toHex((aChar >> 4) & 0xF));
                        outBuffer.append(toHex(aChar & 0xF));
                    } else {
                        outBuffer.append(aChar);
                    }
            }
        }
        return outBuffer.toString();
    }
    /**
     * 从 Unicode 形式的字符串转换成对应的编码的特殊字符串。 如 "\u5c0f" to "小".
     * Converts encoded \\uxxxx to unicode chars
     * and changes special saved chars to their original forms
     * 
     * @param in
     *        Unicode编码的字符数组。
     * @param off
     *        转换的起始偏移量。
     * @param len
     *        转换的字符长度。
     * @param convtBuf
     *        转换的缓存字符数组。
     * @return 完成转换,返回编码前的特殊字符串。
     */
    public static String fromEncodedUnicode(char[] in , int off, int len) {
        char aChar;
        char[] out = new char[len]; // 只短不长
        int outLen = 0;
        int end = off + len;
        while (off < end) {
            aChar = in [off++];
            if (aChar == '\\') {
                aChar = in [off++];
                if (aChar == 'u') {
                    // Read the xxxx
                    int value = 0;
                    for (int i = 0; i < 4; i++) {
                        aChar = in [off++];
                        switch (aChar) {
                            case '0':
                            case '1':
                            case '2':
                            case '3':
                            case '4':
                            case '5':
                            case '6':
                            case '7':
                            case '8':
                            case '9':
                                value = (value << 4) + aChar - '0';
                                break;
                            case 'a':
                            case 'b':
                            case 'c':
                            case 'd':
                            case 'e':
                            case 'f':
                                value = (value << 4) + 10 + aChar - 'a';
                                break;
                            case 'A':
                            case 'B':
                            case 'C':
                            case 'D':
                            case 'E':
                            case 'F':
                                value = (value << 4) + 10 + aChar - 'A';
                                break;
                            default:
                                throw new IllegalArgumentException("Malformed \\uxxxx encoding.");
                        }
                    }
                    out[outLen++] = (char) value;
                } else {
                    if (aChar == 't') {
                        aChar = '\t';
                    } else if (aChar == 'r') {
                        aChar = '\r';
                    } else if (aChar == 'n') {
                        aChar = '\n';
                    } else if (aChar == 'f') {
                        aChar = '\f';
                    }
                    out[outLen++] = aChar;
                }
            } else {
                out[outLen++] = (char) aChar;
            }
        }
        return new String(out, 0, outLen);
    }
}