CODEWITHSUNDEEP
javaarraylisthashmap
user1521385
user1521385

Reputation: 183

implement a hash map that takes in k = Date object v = an array

Hello I would like to implement a Hash map that maps a specific Date to an array of ints. the size of the array is 32

I tried this and it compiles :

HashMap<Date,int[]> coord_map = new HashMap<Date, int[]>();

but I am not sure how this works since I did not give a size for the array of integers.

also I tired this:

int[] arr = new int[32];
for(int i =0; i <32; i++){
arr[i] = 0; // initialize the array to 0. 
}
HashMap<Date, arr> attraction_date = new HashMap<Date, arr>();

this gives me a compiler error "Cannot find a class or type named arr"

thank you

I now have a followup question:

I am successfully using one hash map that takes in a date and maps it to an int array. now I want to use multiple instances of this hashmap. since my project deals with theme park data, there will be one hashmap for every attraction.
so how would I implement an array list of hash maps. To keep track of 20 attractions? If anyone can show me a sample setup code, that initializes everything, that would be helpful.

thank you again,

Upvotes: 1

Views: 342

Answers (2)

jlordo
jlordo

Reputation: 37823

What you have on top is good, you don't need to specify a size. This will work

Map<Date, int[]> coordMap = new HashMap<Date, int[]>();
coordMap.put(aDate, new int[]{1,2});
coordMap.put(anotherDate, new int[]{3,4,5,6});
...

So each value int[] can have a different size.

Upvotes: 3

Ivaylo Strandjev
Ivaylo Strandjev

Reputation: 70989

It depends on what you do. If the problem requires that you have an array of exactly 32 ints then create a wrapper class IntArray32 and use HashMap<Date, IntArray32>. Otherwise what you have written will work, it will simply allow you to have int array of any size as value.

Upvotes: 4

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