java的escape和unescape

/*
* escape()和unescape的用法
*
*/
public static String escape(String src) { 
        int i; 
        char j; 
        StringBuffer tmp = new StringBuffer(); 
        tmp.ensureCapacity(src.length() * 6); 
        for (i = 0; i < src.length(); i++) { 
            j = src.charAt(i); 
            if (Character.isDigit(j) || Character.isLowerCase(j) 
                    || Character.isUpperCase(j)) 
                tmp.append(j); 
            else if (j < 256) { 
                tmp.append("%"); 
                if (j < 16) 
                    tmp.append("0"); 
                tmp.append(Integer.toString(j, 16)); 
            } else { 
                tmp.append("%u"); 
                tmp.append(Integer.toString(j, 16)); 
            } 
        } 
        return tmp.toString(); 
    } 

    public static String unescape(String src) { 
        StringBuffer tmp = new StringBuffer(); 
        tmp.ensureCapacity(src.length()); 
        int lastPos = 0, pos = 0; 
        char ch; 
        while (lastPos < src.length()) { 
            pos = src.indexOf("%", lastPos); 
            if (pos == lastPos) { 
                if (src.charAt(pos + 1) == 'u') { 
                    ch = (char) Integer.parseInt(src 
                            .substring(pos + 2, pos + 6), 16); 
                    tmp.append(ch); 
                    lastPos = pos + 6; 
                } else { 
                    ch = (char) Integer.parseInt(src 
                            .substring(pos + 1, pos + 3), 16); 
                    tmp.append(ch); 
                    lastPos = pos + 3; 
                } 
            } else { 
                if (pos == -1) { 
                    tmp.append(src.substring(lastPos)); 
                    lastPos = src.length(); 
                } else { 
                    tmp.append(src.substring(lastPos, pos)); 
                    lastPos = pos; 
                } 
            } 
        } 
        return tmp.toString(); 
    }