CODEWITHSUNDEEP
androidkotlin
Tigran Babajanyan
Tigran Babajanyan

Reputation: 2025

Remove first element of MutableMap

Have a Mutable Map like this 

val orders: MutableMap<Int, MutableList<MenuItem>>

How can I delete first element of it or remove all by filter?

Upvotes: 0

Views: 2898

Answers (2)

Abhimanyu Seth
Abhimanyu Seth

Reputation: 127

I needed to remove a certain number of elements from a map - didn't matter which ones. This worked for me:

orders.remove(orders.keys.first())

For removing all matching a filter, @Roland has given the various APIs you can use. e.g. to remove all entries having empty list as value:

orders.entries.removeAll { it.value.isEmpty() }

Upvotes: 0

Roland
Roland

Reputation: 23242

Regarding the "remove all by filter" you may be interested in one of the following:

orders.entries.removeIf { /* your predicate */ }
orders.values.removeIf { /* your predicate */ }
orders.keys.removeIf { /* your predicate */ }
// and/or the extension function removeAll:
orders.entries.removeAll { /* your predicate */ }
orders.values.removeAll { /* your predicate */ }
orders.keys.removeAll { /* your predicate */ }

Regarding removing the first I assume you just want any (but at most 1) matching element to remove (not the actual first in a Map). You could probably just iterate/filter, take the first and then simply call remove for it..., e.g.:

val yourMatchingEntry = orders.entries.first { /* your predicate */ }
        .also { orders.entries.remove(it) }

This then just returns any (but 1) of the map entries which match your predicate.

Upvotes: 3

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