JAVA 数组转字符串,用符号分割

需要引入Apache Commons组件中的个commons-lang.jar包：
public static void main(String[] args){
        List<String> ary = Arrays.asList("aa","bb","cc","dd");
        String newStr = StringUtils.join(ary, ",");
        System.out.println(newStr);
}

遍历拼接
public static void main(String[] args){
        List<String> ary = Arrays.asList("aa","bb","cc","dd");

        StringBuffer strbf = new StringBuffer();
        for(int i = 0; i < ary.size(); i++){
            strbf. append(ary.get(i).trim()+",");
        }
        String newStr = strbf.toString();
        String str = newStr.substring(0, newStr.length() - 1);
        System.out.println(str);
}