如何转换成三元运算符？

Question

我有一个if-then-else语句，我想将其转换为三元运算符，但是我不知道为什么我不能这样做。代码如下：

public Movie create(NewMovieDTO newMovieDTO) {
    Movie movieForSaving = NewMovieDTOToMovie.map(newMovieDTO);
    List<Actor> actorsForSaving = new ArrayList<Actor>();

    movieForSaving.getActors().forEach((actor) -> {
        Optional<Actor> actorInDatabase = actorService
            .findByNameAndSurname(actor.getName(), actor.getSurname());

        if(actorInDatabase.isPresent()) {
            actorForSaving.add(actorInDatabase.get());
        } else {
            actorForSaving.add(actor);
        }
    });
    movieForSaving.setActors(actorForSaving);
    return movieRepository.save(movieForSaving);
}

三元运算符的代码是：

public Movie create(NewMovieDTO newMovieDTO) {
    Movie movieForSaving = NewMovieDTOToMovie.map(newMovieDTO);
    List<Actor> actorsForSaving = new ArrayList<Actor>();

    /*Line 1*/ movieForSaving.getActors().forEach((actor) -> {
        Optional<Actor> actorInDatabase = actorService
            .findByNameAndSurname(actor.getName(), actor.getSurname());
        /*Line 2*/(actorInDatabase.isPresent()) ? actorForSaving.add(actorInDatabase.get()) : actorForSaving.add(actor);
    /*Line 3*/});

    movieForSaving.setActors(actorForSaving);
    return movieRepository.save(movieForSaving);
}

IDE给出以下错误：

第1行：此表达式的目标类型必须是功能接口

第2行：此行有多个标记

            - Syntax error, insert "AssignmentOperator Expression" to complete Assignment

            - Syntax error, insert "}" to complete Block

            - actorForSaving cannot be resolved to a variable

            - Syntax error on token(s), misplaced construct(s)

            - actorInDatabase cannot be resolved

            - actorForSaving cannot be resolved

            - Syntax error, insert ";" to complete Statement

第3行：令牌的语法错误，请删除这些令牌。

是否可以在此处执行三元运算符，或者我该如何解决？

非常感谢你的帮助！

Answer 1

actorForSaving.add(actorInDatabase.isPresent() ? actorInDatabase.get() : actor);

三元运算符不能是语句，它是返回内容的表达式。对于您的情况，actorInDatabase.isPresent() ? actorInDatabase.get() : actor返回Actor。

另一个不错的选择是使用Optional#orElse-

actorForSaving.add(actorInDatabase.orElse(actor));