java：不兼容类型：推理变量T具有不兼容的边界等式约束：下限：java.util.List
我试图从流中获取一个列表，但我有一个例外。
这是带有对象列表的Movie对象。
public class Movie { private String example; private List movieTranses; public Movie(String example, List movieTranses){ this.example = example; this.movieTranses = movieTranses; } getter and setter 这是MovieTrans：
public class MovieTrans { public String text; public MovieTrans(String text){ this.text = text; } getter and setter
我在列表中添加元素：
List movieTransList = Arrays.asList(new MovieTrans("Appel me"), new MovieTrans("je t'appel")); List movies = Arrays.asList(new Movie("movie played", movieTransList)); //return a list of MovieTrans List movieTransList1 = movies.stream().map(Movie::getMovieTranses).collect(Collectors.toList());
我有这个编译错误：
Error:(44, 95) java: incompatible types: inference variable T has incompatible bounds equality constraints: MovieTrans lower bounds: java.util.List
map电话
movies.stream().map(Movie::getMovieTranses)
将Stream转换为Stream ，您可以将其收集到List ，而不是List 。
要获取单个List ，请使用flatMap ：
List movieTransList1 = movies.stream() .flatMap(m -> m.getMovieTranses().stream()) .collect(Collectors.toList());
表达式的类型是List ：它是getMovieTranses方法结果的串联。
请改用flatMap ：
List movieTransList1 = movies.stream() .flatMap(m -> m.getMovieTranses().stream()) .collect(Collectors.toList());