A.Iterator迭代器實(shí)現(xiàn) B.增強(qiáng)for循環(huán)實(shí)現(xiàn) C.get()和size()方法結(jié)合實(shí)現(xiàn) D.get()和length()方法結(jié)合實(shí)現(xiàn)
A.HashSet B.TreeSet C.map D.collection
A.HashSet允許存放null值 B.HashSet不允許存放null值 C.TreeSet不允許存放null值 D.TreeSet允許存放null值