相关疑难解决方法(0)

我意识到Java 8 lambda实现可能会发生变化,但在lambda build b39中,我发现只有当lambda表达式返回非void类型时才能省略大括号.例如,这编译:

public class Collections8 {
        public static void main(String[] args) {
                Iterable<String> names = Arrays.asList("Alice", "Bob", "Charlie");
                names.filter(e -> e.length() > 4).forEach(e -> { System.out.println(e); });
        }
}

但删除这样的大括号:

names.filter(e -> e.length() > 4).forEach(e -> System.out.println(e));

给出了错误

Collections8.java:6: error: method forEach in interface Iterable<T> cannot be applied to given types;
        names.filter(e -> e.length() > 4).forEach(e -> System.out.println(e));
                                         ^
  required: Block<? super String>
  found: lambda
  reason: incompatible return type void in lambda expression
  where T is a …