CODEWITHSUNDEEP
javaarrays
nodejs_ios
nodejs_ios

Reputation: 97

Divide array into chunks of 3 and place them into array of arrays?

I've been trying to find a solution to my problem, I have an array of Foods called foods that I want to divide into an array of arrays (foodsArray) so each array contains 3 Food objects. For example: [[Food1, Food2, Food3], [Food4, Food5, Food6]]

I've currenly implemented my problem like that:

Food[] foods = new Food[foodData.length]; //loaded in from a file
List<Food> foodsArray = new ArrayList<Food>();

for(int i=0;i<foods.length;i+=5){
   foodsArray.add(Arrays.copyOfRange(foods, i, Math.min(foods,i+5))); //error is here
   //Output
   System.out.println(Arrays.toString(Arrays.copyOfRange(foods, i, Math.min(foods,i+5))));
}

Current outcome (foodsArray): [[Lcom.company.Food;@3c756e4d, [Lcom.company.Food;@7c0e2abd, [Lcom.company.Food;@48eff760, [Lcom.company.Food;@402f32ff]

Expected outcome (foodsArray):

[[com.company.Food@458ad742, com.company.Food@48eff760, com.company.Food@402f32ff],
 [com.company.Food@6d8a00e3, com.company.Food@548b7f67, com.company.Food@7ac7a4e4],
 [com.company.Food@5dfcfece]]

Upvotes: 0

Views: 83

Answers (2)

Oleksii Zghurskyi
Oleksii Zghurskyi

Reputation: 4365

Late to the party, but here is Java 8 solution:

Food[][] partition(Food[] foods, int groupSize) {
  return IntStream.range(0, foods.length)
          .boxed()
          .collect(Collectors.groupingBy(index -> index / groupSize))
          .values()
          .stream()
          .map(indices -> indices
                  .stream()
                  .map(index -> foods[index])
                  .toArray(Food[]::new))
          .toArray(Food[][]::new);
}

Effectively, partition method allows to partition array into groups of arbitrary size groupSize.

In case of the question, the desired result will be obtained by calling:

Food[][] result = partition(foods, 3);

Upvotes: 0

MWB
MWB

Reputation: 1879

What about this! You just iterate over the array and add three of them to a list and, after each three, add the list to another list, resetting the initial list.

ArrayList<ArrayList<Food>> result = new ArrayList<>();
ArrayList<Food> subArray = new ArrayList<>();
for (int i = 0; i < foods.length; i++) {
    subArray.add(foods[i]);
    if (i % 3 == 2) {
        result.add(subArray);
        subArray = new ArrayList<>();
    }
}

Nice and simple. As Nicholas K suggested, I am using a List<List<Food>>

Upvotes: 3

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