CODEWITHSUNDEEP
javacollections
amphibient
amphibient

Reputation: 31338

Map implementation that keeps entries in the order of addition

I need a key-value pair data structure which guarantees the retrieval of entries in the order in which they were added, much like ArrayList or Vector for just singular entries. Think of it as an ArrayList that enables key-value pairs. Keep in mind, the TreeMap will not do because the sorting does not go by the value of the key but by the time of insertion. Is there a Java Collection that meets these requirements? I browsed different Map implementations but couldn't find any that match.

I understand I can define my class that takes the key and the value and put it in an ArrayList but that is only option B to a class described above.

Upvotes: 1

Views: 977

Answers (3)

user949300
user949300

Reputation: 15729

Use java.util.LinkedHashMap Javadocs here

"This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map (insertion-order)"

Upvotes: 0

Adam Siemion
Adam Siemion

Reputation: 16039

I need a key-value pair data structure which guarantees the retrieval of entries in the order in which they were added,

LinkedHashMap

Hash table and linked list implementation of the Map interface, with predictable iteration order.

Upvotes: 4

AllTooSir
AllTooSir

Reputation: 49432

Are you looking for LinkedHashMap ?

Hash table and linked list implementation of the Map interface, with predictable iteration order.

You can also look into the Guava's ImmutableMap if it suits your purpose.

An immutable, hash-based Map with reliable user-specified iteration order. Does not permit null keys or values.

Upvotes: 6

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