CODEWITHSUNDEEP
javacollections
John Vasiliou
John Vasiliou

Reputation: 997

Choosing the correct collection

I'm designing a system which needs a specific collection, it is written in Java. I need to store the history of prices of stock (dates and time).

One stock can have multiple dates and times as I want to show the previous prices.

Which collection would I use to map a stock id to multiple dates AND times?

I know there are HashTables, but I can't see how they will work as they still take only a key and a value. I have a stock class, within it I want a collection which takes and a value and a value.

Upvotes: 2

Views: 506

Answers (5)

Don McCurdy
Don McCurdy

Reputation: 11960

You could create a hashtable containing another type of collection. For example, if your stock IDs are Integers and being able to see the history of prices chronologically is your main use case, create a hashtable of arraylists, and keep the arraylists sorted by date:

HashMap< Integer, ArrayList<Stock> > stockCollection = new HashMap< Integer, ArrayList<Stock> >();

Or, if you really need to be able to access the stock price for a particular date in O(1) time, create a hashtable of hashtables:

HashMap< Integer, HashMap<Date, Stock> > stockCollection = new HashMap< Integer, HashMap<Date, Integer> >();

Upvotes: 1

kosa
kosa

Reputation: 66637

One option would be using google guava multi-map (If you are ok to include third party jars).

multi-map allows you to add elements with same key.

Here is simple tutorial.

EDIT:

If not allowed to use guava, then another option would be:

HashMap<String, ArrayList<Stock>> map = HashMap<String, ArrayList<Stock>>()

Here Stock is simple POJO class with timeStamp and stock symbol.

Upvotes: 4

Addict
Addict

Reputation: 823

You can use HashMap where key will be stockid and value will be arraylist of the objects which contain date and time.

Map<Integer, ArrayList<Price>> anyname = new HashMap<Integer, ArrayList<Price>>();

Upvotes: 1

FThompson
FThompson

Reputation: 28687

You could use a map of the stock IDs as the key, and a list of prices as the value.

Map<Integer, List<Price>> stocks = new HashMap<Integer, List<Price>>();

Upvotes: 2

Juvanis
Juvanis

Reputation: 25950

Suppose you have a Price object, then you can use a map like this:

HashMap<String, ArrayList<Price>> map = HashMap<String, ArrayList<Price>>();

Of course you can change your key type to your own.

Upvotes: 2

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