去除一个list包含另一个list的数据

List<String> list1 = Arrays.asList("a","b","c","d");
List<String> list2 = Arrays.asList("a","b","c","e");

HashSet<String> hashSet1 = new HashSet<String>(list1);
HashSet<String> hashSet2 = new HashSet<String>(list2);

//hashSet1移除hashSet2中相同的数据
hashSet1.removeAll(hashSet2);

//转换字符串
String.join(",",hashSet1);