What are the algorithem and container to be used for this problem?

Question

Say I have a class with the following properties:
groupMonth //String (jan,feb,mar�)
accumulatedLasyYear //double
accumulatedThisYear //double
What will be the best container/algorithm to use for objects from the class above so I can have them sorted by month (I know it�s a string) AND GROUP the months together (and the accumulated as well)
Example:
Jan 4 8
Feb 2 3
Mar 5 2
Jan 3 5
Feb 4 2
Mar 9 3
The output should be:
Jan 7 13 //(4+3, 8+5)
Feb 6 5
Mar 14 5
Thanks for any thought�

Answer 1

I'd suggest a java.util.Map<String, Set<WhateverClassYouveDefined>>. The keys are the year, the values are Sets containing all objects of that year. Iterate through your list of objects and group them into the right set using the map.
Then I'd suggest looping through the keys to get each month's worth. Since you know what all the keys will be in advance, and there's only twelve of them, create an array of the twelve month strings. Loop through that array, and for each value grab the corresponding Set from the map.
Then for each set you get, iterate through its contents, get the values, and add them.
Then just print the month and the sums of values from the set, and go on to the next month.