（1）List<对象>转Map<String, String>、List<String>

List<Task> taskList = new ArrayList<>();
Map<String, String> map = taskList.stream().collect(Collectors.toMap(Task::getDeviceId, Task::getTaskId, (existing, replacement) -> existing));
List<String> list = taskList.stream().map(Task::getDeviceId).collect(Collectors.toList());

（2）List<Map<String, Object>>转Map<String, String>、List<String>

List<Map<String, Object>> taskList = new ArrayList<>();
Map<String, String> map = taskList.stream().collect(Collectors.toMap(item -> (String) item.get("device_id"), item -> (String) item.get("task_id"), (oldValue, newValue) -> oldValue));
List<String> list = taskList.stream().map(item -> (String) item.get("device_id")).collect(Collectors.toList());