问题
I would like to flatten arbitrary deeply nested collections/structures of elements of some type T in Java, optimally with
- only having a live view and not a copied collection;
- not only handling Collections, but also Iterator, arrays of T of arbitrary dimension, Iterable, and all these structures arbitrarily mixed and nested;
- statical type-safety.
Is there a java library which can handle this?
Guava seems to only handle one nesting level, i.e. Collection<Collection<T>> --flatten--> Collection<T>.
lambdaj looks promising: can I somehow combine on(), asIterator() and flattenIterator() to achieve this? In a statically type-safe manner?
回答1:
Guava will probably support this eventually :
http://code.google.com/p/guava-libraries/issues/detail?id=174
(It might be easiest to read that from the bottom up, since the thinking on it has shifted a few times over its lifetime.)
回答2:
Not based on either of the above, but perhaps a DeepIterator class that is constructed with a Collection whose next() method looks at the next Object and if it is a instanceof Collection then pushes the current iterator on Stack and recurses into that Collection's iterator.
回答3:
I think this may help: Arrays.deepToString(myCollection.toArray())
来源：https://stackoverflow.com/questions/7431006/type-safe-flattening-of-nested-collections-structures-in-java