public String arrayToString() {
	List<Character> result = new ArrayList<Character>();
	result.add('a');
	result.add('b'); //['a', 'b']
	StringBuffer resultStr = new StringBuffer();// 利用StringBuffer将arraylist转为string
    for (int i = 0; i < result.size(); i++) {
        resultStr.append(result.get(i));
    }
    return resultStr.toString();
}

public String arrayToString() {
	List<Character> result = new ArrayList<Character>();
	result.add('a');
	result.add('b'); //['a', 'b']
	String resultStr = StringUtils.join(result, ",");
    return resultStr;
}