Collections quick review

There are times in our developer lives when we just settle with a range of implementations without thinking of the reasons behind it, or without having any valid argument in order to use one implementation over another.

Some time ago I was having a discussion with a friend [which is a big data developer] about the importance of choosing the right collection. He gave an example on how using the wrong implementation a job took over 3 hours, after changing the implementation of the collection used the same job needed 5 minutes to complete.

Below can be seen a table with basic information about different implementations of collections

Implementation Ordered Sorted Syncronized Nulls Notes
HashMap One null key andno null values
Hashtable* No null keys and no null values
TreeMap Accepts nulls as keys and value
LinkedHashMap Accepts nulls as keys and value Faster iterations than HashMap but slower inserts and remove
HashSet Accepts null
TreeSet Accepts null
LinkedHashSet Accepts null
ArrayList Accepts null Fast iterations
Vector Accepts null
LinkedList Accepts null Fast iterations and deletion
PriorityQueue Accepts null

* There is not a typo: Hashtable is the special kid that does not have camel case

PS: This is just a quick review for more about how each works, I suggest visiting the API.

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