十六進制高低位轉換，返回十進制數

/**
     * 十六進制高低位轉換，返回十進制數
     * @param str
     * @return
     */
    public static String decodeHexStringToDec(String str) {
        str =HighLowHex(spaceHex(str));
        String value =new BigInteger(str, 16).toString();
        return value;
    }
    
    /**
     * 十六進制數隔空位
     * @param str
     * @return
     */
    private static String spaceHex(String str){
        char[] array= str.toCharArray();
            if(str.length()<=2) return str;
                StringBuffer buffer =new StringBuffer();
                for(int i=0;i<array.length;i++){
                int start =i+1;
                if(start%2==0){
                    buffer.append(array[i]).append(" ");
                }else{
                    buffer.append(array[i]);
                }
            }
        return buffer.toString();
    }
    
    /**
     * 高位16進制轉低位
     * @param str
     * @return
     */
    private static String HighLowHex(String str){
        if(str.trim().length()<=2) return str;
        List<String> list = Arrays.asList( str.split(" "));
        Collections.reverse(list);
        StringBuffer stringBuffer = new StringBuffer();
        for(String string:list){
            stringBuffer.append(string);
        }
        return stringBuffer.toString();
    }