Question

Write a Java program that takes an ArrayList<Integer>,  adds k copies of it at the end, and returns the expanded ArrayList.  The total size will be (k+1) * n.  

public ArrayList<Integer> makeCopies(ArrayList<Integer>, int k) {

}

Example: ArrayList<Integer> has (3,7,4) and k = 2, then the returned, expanded ArrayList will have (3,7,4,3,7,4,3,7,4).  The total size is (k+1)*n = (2+1)*3= 9.

Answer 1

public ArrayList<Integer> makeCopies(ArrayList<Integer> list, int k) {
    ArrayList<Integer> result = new ArrayList<>(list);
    for (int i = 0; i < k; i++) {
        result.addAll(list);
    }
    return result;
}

import java.util.ArrayList;

public class ArrayListCopies {

    public ArrayList<Integer> makeCopies(ArrayList<Integer> list, int k) {
        ArrayList<Integer> result = new ArrayList<>(list);
        for (int i = 0; i < k; i++) {
            result.addAll(list);
        }
        return result;
    }

    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(3);
        list.add(7);
        list.add(4);
        System.out.println(list);
        System.out.println(new ArrayListCopies().makeCopies(list, 2));
    }
}