// 方法一：
    public String listToString1(List list, char separator) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < list.size(); i++) {
            sb.append(list.get(i)).append(separator);

        }
        return sb.toString().substring(0, sb.toString().length() - 1);
    }

    // 方法二：
    public String listToString2(List list, char separator) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < list.size(); i++) {
            if (i == list.size() - 1) {
                sb.append(list.get(i));
            } else {
                sb.append(list.get(i));
                sb.append(separator);
            }
        }
        return sb.toString();
    }

    // 方法三：
    public String listToString3(List list, char separator) {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < list.size(); i++) {
            sb.append(list.get(i));
            if (i < list.size() - 1) {
                sb.append(separator);
            }
        }
        return sb.toString();
    }

    // 方法四：
    public class Separator {
        private String next = "";
        private String separator;

        public Separator(String separator) {
            this.separator = separator;
        }

        public String get() {
            String result = next;
            next = separator;
            return result;
        }
    }

    public String listToString(List<String> list, Separator separator) {
        StringBuilder sb = new StringBuilder();
        for (String s : list) {
            if (s != null && !"".equals(s)) {
                sb.append(separator.get()).append(s);
            }
        }
        return sb.toString();
    }

    // 方法五：
    public String listToString(List list, char separator) {
        return org.apache.commons.lang.StringUtils.join(list.toArray(), separator);
    }