String[]、String、List<String>互转

String[] ids 

String id 

List<String> idList 

1、String[]转String

String id= String.join(",", ids);

2、String转String[]

String[] ids = id.split(",");

3、String[]转List<String>

List<String> idList = Arrays.asList(ids);

4、List<String>转String[]

　　String[] ids= idList.toArray(new String[idList.size()]);

5、String转List<String>

List<String> idList = Arrays.asList(id.split(","));

6、List<String>转String

String id= String.join(",", idList);

7、List<T>转String

String receiver = zhizhaokeList.stream().map(SysUser::getUsername).collect(Collectors.joining(","));
8、List<T>转List<String>

List<String> reportIds1 = tList.stream().map(SysUser::getUsername).collect(Collectors.toList()).stream().distinct().collect(Collectors.toList());