public String[] extractMinimumParentheses(){
        Pattern pattern = Pattern.compile("[(][0-9¥+¥-¥*/]+[)]");
        Matcher matcher = pattern.matcher(expression);
        String[] extractedExpression = new String[matcher.groupCount()];

        if (matcher.find()) {
            for(int i = 0; i < matcher.groupCount(); i++) {
                extractedExpression[i] = matcher.group(i);
            }
        }
        else {
            throw new IllegalArgumentException("No match found.");
        }
        return new String[]{ };
    }