Question

Implement the following methods (based on ArrayLists): (JAVA)
a) merge method that takes two ArrayLists as input and returns the merged ArrayList

containing the elements from both the input lists.
b) enumerate method that takes an ArrayList as input and prints the enumerated

contents of the input list.
c) reverse method that takes an ArrayList as input and returns an ArrayList with the

contents of input list in reverse order.
Test your method implementations.

Answer 1

import java.util.ArrayList;

import java.util.Arrays;

import java.util.Collections;

public class Main {

public static ArrayList<Integer> merge(ArrayList<Integer> a1, ArrayList<Integer> a2) {

ArrayList<Integer> res = new ArrayList<>();

res.addAll(a1);

res.addAll(a2);

return res;

}

public static void enumerate(ArrayList<Integer> a) {

for(int elem : a) {

System.out.print(elem + " ");

}

System.out.println("\n");

}

public static ArrayList<Integer> reverse(ArrayList<Integer> a) {

Collections.reverse(a);

return a;

}

public static void main(String[] args) {

ArrayList<Integer> a1 = new ArrayList<>();

ArrayList<Integer> a2 = new ArrayList<>();

a1.addAll(Arrays.asList(1, 2, 3, 4, 5));

a2.addAll(Arrays.asList(10, 20, 30, 40, 50));

enumerate(a1);

enumerate(a2);

ArrayList<Integer> merged = merge(a1, a2);

enumerate(merged);

reverse(merged);

enumerate(merged);

}

}