Java中的类型安全map-reduce

Question

如何编写集合的类型安全映射器/转换器?

class Bean {
 public int value;
}
List<Bean> beans = ..
List<Integer> ints = Lib.map(beans, b => b.value);

使用Apache Commons-Collections，它看起来像这样:

    Collection<Integer> ints = CollectionUtils.collect(beans, new Transformer() {
        @Override
        public Object transform(Object input) {
            return null; //cast here, dereference etc.
        }
    });

但是这不是类型安全的

Answer 1

查看番石榴的Lists类:

public static <F,T> List<T> transform(List<F> fromList,
                  Function<? super F,? extends T> function)

API docs here