1、将逗号分隔的字符串转换为List
String str = "a,b,c";
List<String> result = Arrays.asList(str.split(","));
2、将List转换为逗号分隔的字符串
(1) 利用Guava的Joiner
List<String> list = new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
String str = Joiner.on(",").join(list);
(2)利用Apache Commons的StringUtils
List<String> list = new ArrayList<String>();
list.add("a");
list.add("b");
list.add("c");
String str = StringUtils.join(list.toArray(), ",");