[bo]以下是引用 [un]Still_Man[/un] 在 2008-2-3 23:08 的发言：[/bo]
Collection是Java中的集合接口,而Collections才是Java中的集合类,LZ可以根据这个查查看,具体也不好说
Collection是Java中的集合接口,而Collections才是Java中的集合类,LZ可以根据这个查查看,具体也不好说
哦~谢谢！
> public class TreeSet<E>
> extends AbstractSet<E>
> implements SortedSet<E>, Cloneable,
Generic class declaration: The "parameter" E is replaced by the programmer when using the class, e.g. TreeSet<String>.
> public boolean addAll(Collection<? extends E> c)
Wildcard generic parameter: It means that the parameter can be any
generic Collection where the parametrized type extends the collection.
So if you have
class Foo { ...
class Fie extends Foo { ...
set = new TreeSet<Foo>();
otherCollection = new ArrayList<Fie>();
you can do a
set.addAll(otherCollection);
because the generic parameter for the second declaration is a class
that extends the parameter class of the first.
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[ 本帖最后由 sunboy_2050 于 2011-11-18 18:03 编辑 ]