Map<String, Object> map = new HashMap<>();

        List<String> list = new ArrayList<>();

        map.forEach((k, v) -> {

            list.add(v.toString());

        });

@Data
public class TestEntity {

  private String code;

  private String name;

}

        List<TestEntity> list = new ArrayList<>();

        Map<String, TestEntity > map = list.stream().collect(

          Collectors.toMap(item -> ((TestEntity )item).getCode,

                  item -> (TestEntity)item)

        );