问题描述
我的用例需要一个 Stack
数据结构.我应该能够将项目推送到数据结构中,并且我只想从堆栈中检索最后一项.JavaDoc for Stack 说:
I need a Stack
data structure for my use case. I should be able to push items into the data structure and I only want to retrieve the last item from the Stack. The JavaDoc for Stack says :
一组更完整和一致的 LIFO 堆栈操作是由 Deque 接口及其实现提供,应该优先于此类使用.例如:
Deque<Integer> stack = new ArrayDeque<>();
我绝对不想在这里同步行为,因为我将在方法本地使用这个数据结构.除此之外,为什么我应该更喜欢 Deque
而不是 Stack
?
I definitely do not want synchronized behavior here as I will be using this datastructure local to a method . Apart from this why should I prefer Deque
over Stack
here ?
P.S:来自 Deque 的 javadoc 说:
P.S: The javadoc from Deque says :
双端队列也可以用作 LIFO(后进先出)堆栈.这应优先使用接口而不是旧的 Stack 类.
推荐答案
一方面,它在继承方面更明智.在我看来,Stack
扩展 Vector
的事实真的很奇怪.在 Java 早期,IMO 过度使用继承 - Properties
是另一个例子.
For one thing, it's more sensible in terms of inheritance. The fact that Stack
extends Vector
is really strange, in my view. Early in Java, inheritance was overused IMO - Properties
being another example.
对我来说,您引用的文档中的关键词是一致.Deque
公开了一组操作,这些操作都是关于能够从集合的开头或结尾获取/添加/删除项目、迭代等 - 就是这样.故意无法按位置访问元素,Stack
暴露了 因为它是 Vector
的子类.
For me, the crucial word in the docs you quoted is consistent. Deque
exposes a set of operations which is all about being able to fetch/add/remove items from the start or end of a collection, iterate etc - and that's it. There's deliberately no way to access an element by position, which Stack
exposes because it's a subclass of Vector
.
哦,而且 Stack
没有接口,所以如果你知道你需要 Stack
操作,你最终会提交到一个特定的具体类,这通常不是好主意.
Oh, and also Stack
has no interface, so if you know you need Stack
operations you end up committing to a specific concrete class, which isn't usually a good idea.
正如评论中指出的,Stack
和 Deque
具有反向迭代顺序:
Also as pointed out in the comments, Stack
and Deque
have reverse iteration orders:
Stack<Integer> stack = new Stack<>();
stack.push(1);
stack.push(2);
stack.push(3);
System.out.println(new ArrayList<>(stack)); // prints 1, 2, 3
Deque<Integer> deque = new ArrayDeque<>();
deque.push(1);
deque.push(2);
deque.push(3);
System.out.println(new ArrayList<>(deque)); // prints 3, 2, 1
这也在 Deque.iterator():
以正确的顺序返回此双端队列中元素的迭代器.元素将按从第一个(头)到最后一个(尾)的顺序返回.
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