在给定值的情况下查找地图中的关键字 [英] Finding the key in a map, given the value
问题描述
您好我有这样的地图:
[this:0,is:1,a:2,file: 3,anotherkey:4,aa:5]
我希望能找到 key
给出地图的值
。例如,如果给定值 5
,我需要从地图返回 aa
。
是否有可能?
我不知道是否有直接的方法可以获得一个给定值的关键字,但使用 Map#find
得到一个map条目,然后得到它的值应该足够了:
def keyForValue(map,value){
map.find {it.value == value} ?. key
}
def map = [a: 1,b:2,c:3]
assert keyForValue(map,2)=='b'
assert keyForValue(map,42)== null
一般而言,地图不需要在其条目之间存在顺序关系,但Groovy文字地图的默认实现是LinkedHashMap,它 是有序的,所以当使用这些映射时, keyForValue
总会产生一个值的第一个键s。
Hi I have a map like this :
[this:0, is:1, a:2, file:3, anotherkey:4, aa:5]
I wish I could find the key
's given the value
of a map. For example, if the value 5
is given I need to return aa
from the map.
Is that possible?
I don't know if there's a direct method to get a key for a given value, but using Map#find
to get a map entry and then get its value should be enough:
def keyForValue(map, value) {
map.find { it.value == value }?.key
}
def map = [a: 1, b: 2, c: 3]
assert keyForValue(map, 2) == 'b'
assert keyForValue(map, 42) == null
In general, maps don't need to have an order relation between their entries, but the default implementation for Groovy's literal maps is LinkedHashMap, which is ordered, so the keyForValue
will always yield the first key for a value when using those maps.
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