Best data structure for maintaining a list of object-types sorted by frequency

Question

So, I'm going through a long list with different types of things. Let's say that it has names of different kinds of foods. The list might look something like this:

olive
potato
strawberry
potato
potato
strawberry

I want to store each object type and the number of times that object type occurs. Moreover, I cannot enumerate all of the object types in advance. I don't know what all of the foods will be beforehand.

I want to have something like this as the output:

potato (3)
strawberry (2)
olive (1)

Basically, a list of the object types in order of their frequency. What's the best data structure for this? Are there any built-in classes in Java that I could use that would prevent me from having to reinvent the wheel?

Answer 1

You can use HashMap<K,V>

Map<String,int> map = new HashMap<String,int>();

Answer 2

I would use a dictionary-like structure. Then basically your algorithm would look like this:

-Begin Loop
    If current element not a key in dictionary:
        dictionary(element) -> 0 (Dictionary at key 'element' refers to 0)
    Else:
        dictionary(element)++ (increment dictionary at key)

Then you could later loop through the keys and find their frequencies.

Michael G.