Question

我有一个要保存到数据库中的ID列表集合

if(!session.ids)
session.ids = []

session.ids.add(params.id)

我发现该列表有重复项，例如

[1, 2, 4, 9, 7, 10, 8, 6, 6, 5]

然后我想通过应用类似的东西删除所有重复项：

session.ids.removeAll{ //some clousure case }

我发现只有这个：

http://groovy.codehaus.org/groovy-jdk/java/util/Collection.html

Answer 1

我不是一个Groovy人，但我相信你可以这样做：

[1, 2, 4, 9, 7, 10, 8, 6, 6, 5].unique { a, b -> a <=> b }

您是否尝试过session.ids.unique()？

Answer 2

怎么样：

session.ids = session.ids.unique( false )

<强>更新
区分unique()和unique(false)：第二个不修改原始列表。希望有所帮助。

def originalList = [1, 2, 4, 9, 7, 10, 8, 6, 6, 5]

//Mutate the original list
def newUniqueList = originalList.unique()
assert newUniqueList == [1, 2, 4, 9, 7, 10, 8, 6, 5]
assert originalList  == [1, 2, 4, 9, 7, 10, 8, 6, 5]

//Add duplicate items to the original list again
originalList << 2 << 4 << 10

// We added 2 to originalList, and they are in newUniqueList too! This is because
// they are the SAME list (we mutated the originalList, and set newUniqueList to
// represent the same object.
assert originalList == newUniqueList

//Do not mutate the original list
def secondUniqueList = originalList.unique( false )
assert secondUniqueList == [1, 2, 4, 9, 7, 10, 8, 6, 5]
assert originalList     == [1, 2, 4, 9, 7, 10, 8, 6, 5, 2, 4, 10]

Answer 3

使用唯一

def list = ["a", "b", "c", "a", "b", "c"]
println list.unique()

这将打印

[a, b, c]

Answer 4

def unique = myList as Set

将'myList'转换为Set。当您使用复杂（自定义类）时，请确保您已正确考虑正确实现hashCode（）和equals（）。

Answer 5

如果session.ids包含唯一ID，那么您可以这样做：

if(!session.ids)
  session.ids = [] as Set

然后当你这样做：

session.ids.add(params.id)

不会添加重复项。

您也可以使用以下语法：

session.ids << params.id

Answer 6

合并两个数组并使元素唯一：

def arr1 = [1,2,3,4]
def arr2 = [1,2,5,6,7,8]
def arr3 = [1,5,6,8,9]

让我们看一下合并：

arr1.addAll(arr2, arr3) 
// [1, 2, 3, 4, [1, 2, 5, 6, 7, 8], [1, 5, 6, 8, 9]]
def combined = arr1.flatten() 
// [1, 2, 3, 4, 1, 2, 5, 6, 7, 8, 1, 5, 6, 8, 9]
def combined = arr1.flatten().unique()
// [1, 2, 3, 4, 5, 6, 7, 8, 9]


def combined = (arr1 + arr2 + arr3).flatten().unique()

def combined = (arr1 << arr2 << arr3).flatten().unique()

def combined = arr1.plus(arr2).plus(arr3).flatten().unique()

输出将是：

println combined
[1, 2, 3, 4, 5, 6, 7, 8, 9]

如何从groovy中的列表中删除重复值

6 个答案: