Set<E>接口和List<E>接口的根本区别是什么?


当前回答

Java中List和Set之间的一些值得注意的区别如下:

1) Java中的List和Set之间的基本区别是允许重复元素。Java中的List允许重复,而Set不允许任何重复。如果在Set中插入duplicate,它将替换旧的值。Java中Set的任何实现都只包含唯一的元素。

2) Another significant difference between List and Set in Java is order. List is an Ordered Collection while Set is an unordered Collection. List maintains insertion order of elements, means any element which is inserted before will go on lower index than any element which is inserted after. Set in Java doesn't maintain any order. Though Set provide another alternative called SortedSet which can store Set elements in specific Sorting order defined by Comparable and Comparator methods of Objects stored in Set.

3) Java中比较流行的List接口实现有ArrayList, Vector和LinkedList。而流行的Set接口实现包括HashSet, TreeSet和LinkedHashSet。

很明显,如果你需要维护插入顺序或对象,你的集合可以包含重复的列表是一种方法。另一方面,如果您的要求是保持唯一的集合,没有任何重复,那么Set是最好的方法。

其他回答

Factor List Set
Is ordered grouping elements? YES NO
Provides positional access by index? YES NO
Can store duplicate elements? YES NO
Can store multiple null elements? YES NO
Childs: ArrayList, LinkedList, Vector, and Stack HashSet and LinkedHashSet

List Vs Set

1) Set不允许重复。列表允许重复。基于Set的实现,它还维护插入顺序。

LinkedHashSet。它维护插入顺序。请参考此处

2)包含方法。根据集合的性质,它将为访问提供更好的性能。最好的情况是o(1)但是List有调用contains的性能问题。

这可能不是您想要的答案,但是集合类的JavaDoc实际上非常具有描述性。复制/粘贴:

An ordered collection (also known as a sequence). The user of this interface has precise control over where in the list each element is inserted. The user can access elements by their integer index (position in the list), and search for elements in the list. Unlike sets, lists typically allow duplicate elements. More formally, lists typically allow pairs of elements e1 and e2 such that e1.equals(e2), and they typically allow multiple null elements if they allow null elements at all. It is not inconceivable that someone might wish to implement a list that prohibits duplicates, by throwing runtime exceptions when the user attempts to insert them, but we expect this usage to be rare.

1.List允许重复值,set不允许重复值

2.List维护您在列表中插入元素的顺序 Set不能维持秩序。 3.List是一个有序的元素序列,而Set是一个无序的元素列表。

List

是元素的有序分组。 List用于收集重复的元素。 新方法在List中定义 接口。

Set

是元素的无序分组。 Set用于收集没有重复项的元素。 在Set接口中没有定义任何新方法,因此我们只能对Set子类使用Collection接口方法。