Question

• (Maximum element in ArrayList) Write the following method that returns the maximum value in an ArrayList of integers. The method returns null if the list is null or the list size is 0.
• public static Integer max(ArrayList<Integer> list)
• Write a test program that prompts the user to enter a sequence of numbers ending with 0, and invokes this method to return the largest number in the input.
• Use inheritance and polymorphism approach.

Answer 1

//MaximumArrayList.java
import java.util.ArrayList;
public class MaximumArrayList {
    public static Integer max(ArrayList<Integer> list){
        if(list==null || list.size()==0){
            return null;
        }
        else{
            Integer m = list.get(0);
            for(int i = 1;i<list.size();i++){
                if(m < list.get(i)){
                    m = list.get(i);
                }
            }
            return m;
        }
    }

    public static void main(String[] args) {
        ArrayList<Integer> list = new ArrayList<>();
        list.add(4);
        list.add(1);
        list.add(5);
        list.add(2);
        list.add(3);

        System.out.println("Max element: "+max(list));
    }
}