ASCIIコードの変換

public class Native2AsciiUtils {
    /** 
     * prefix of ascii string of native character 
     */  
    private static String PREFIX = "\\u";  
  
    /** 
     * Native to ascii string. It's same as execut native2ascii.exe. 
     * @param str native string 
     * @return ascii string 
     */  
    public static String native2Ascii(String str) {  
        char[] chars = str.toCharArray();  
        StringBuilder sb = new StringBuilder();  
        for (int i = 0; i < chars.length; i++) {  
            sb.append(char2Ascii(chars[i]));
        }  
        return sb.toString();
    }  
  
    /** 
     * Native character to ascii string. 
     * @param c native character 
     * @return ascii string 
     */  
    private static String char2Ascii(char c) {
        if (c > 255) {  
            StringBuilder sb = new StringBuilder();  
            sb.append(PREFIX);
            int code = (c >> 8);  
            String tmp = Integer.toHexString(code);  
            if (tmp.length() == 1) {  
                sb.append("0");
            }
            sb.append(tmp);
            code = (c & 0xFF);
            tmp = Integer.toHexString(code); 
            if (tmp.length() == 1) {  
                sb.append("0");  
            }
            sb.append(tmp);  
            return sb.toString();  
        } else {  
            return Character.toString(c);  
        }  
    }  
  
    /** 
     * Ascii to native string. It's same as execut native2ascii.exe -reverse. 
     * @param str ascii string 
     * @return native string 
     */  
    public static String ascii2Native(String str) {  
        StringBuilder sb = new StringBuilder();  
        int begin = 0;  
        int index = str.indexOf(PREFIX);  
        while (index != -1) {  
            sb.append(str.substring(begin, index));  
            sb.append(ascii2Char(str.substring(index, index + 6)));  
            begin = index + 6;  
            index = str.indexOf(PREFIX, begin);  
        }  
        sb.append(str.substring(begin));  
        return sb.toString();  
    }  
  
    /** 
     * Ascii to native character. 
     * @param str ascii string 
     * @return native character 
     */  
    private static char ascii2Char(String str) {  
        if (str.length() != 6) {  
            throw new IllegalArgumentException(  
                    "Ascii string of a native character must be 6 character.");  
        }  
        if (!PREFIX.equals(str.substring(0, 2))) {  
            throw new IllegalArgumentException(  
                    "Ascii string of a native character must start with \"\\u\".");  
        }  
        String tmp = str.substring(2, 4);  
        int code = Integer.parseInt(tmp, 16) << 8;  
        tmp = str.substring(4, 6);  
        code += Integer.parseInt(tmp, 16);  
        return (char) code;  
    } 
}