List是项的有序分组 Set是一个无序的项目分组，不允许重复(通常)

从概念上讲，我们通常将允许重复的无序分组称为Bag，而不允许重复的无序分组称为Set。

嗨，已经给出了这么多答案，让我指出一些到目前为止没有提到的地方:

大多数的List实现(ArrayList,Vector)实现了RandomAccess接口，这是一个快速访问的标记接口。Set的实现都没有这样做。 List使用一个特殊的迭代器，称为ListIterator，它支持双向迭代。Set使用只支持单向迭代的迭代器 HashSet占用的内存是ArrayList的5.5倍 相同数量的元素。

这里有一个关于groovy的明确例子。我创建了一个集合和一个列表。 然后我尝试在每个列表中存储20个随机生成的值。生成的值范围为0 ~ 5

s = [] as Set
l = []

max = 5
print "random Numbers :"
20.times{
e = (int)Math.random()*max
s << e
l << e
print "$e, "
}


println "\n"
println "Set : $s "
println "list : $l

结果:

随机数:4,1,4,0,1,2,4,0,0,0,3,4,2,0,4,4,0,4,0,0,1,3,1,3

集合:[4,1,0,2,3]

列表:[4 1 4 0,1,2,4,0,0,3、4、3、2 0 4 0,1,3,1,3)

你可以看到区别在于:

Set不允许重复值。 列表允许重复值。

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.

主题名称:列表VS集

我刚刚介绍了Java中最重要的主题——集合框架。我想和你分享我关于收藏的一点知识。其中最重要的是列表、集合、映射。让我们从List和Set开始。

List与Set的区别:

List is a collection class which extends AbstractList class where as Set is a collection class which extends AbstractSet class but both implements Collection interface. List interface allows duplicate values (elements) whereas Set interface does not allow duplicate values. In case of duplicate elements in Set, it replaces older values. List interface allows NULL values where as Set interface does not allow Null values. In case of using Null values in Set it gives NullPointerException. List interface maintains insertion order. That means the way we add the elements in the List in the same way we obtain it using iterator or for-each style. Whereas Set implementations do not necessarily maintain insertion order. (Although SortedSet does using TreeSet, and LinkedHashSet maintains insertion order). List interface has its own methods defined whereas Set interface does not have its own method so Set uses Collection interface methods only. List interface has one legacy class called Vector whereas Set interface does not have any legacy class Last but not the least... The listIterator() method can only be used to cycle through the elements within List Classes whereas we can use iterator() method to access Set class elements

还有什么要补充的吗?请让我知道。

谢谢。