using arraylist in java, write a document management system program

package com.mycompany.cis104;

import java.util.Date;

/**
 *
 * @author ads21
 */
    
class Document
{
private String[] authors;
private Date date;
private int authorsCounter;
public Document()
{
    authors=new String[5];
    authorsCounter=0;
}
public String[] getAuthors()
{
    return authors;
}

public void addAuthor(String name)
{
    if(authorsCounter<authors.length)
    {
    authors[authorsCounter]=name;
    authorsCounter++;
    }
    else System.out.println("authors array is full!");
}

public Date getDate()
{
    return date;
}
}
    
class Book extends Document
{

    private String title;
    
    public String getTitle()
    {
        return title;
    }
    
}
class Email extends Document
{
private String subject;
private String[] to;

public String getSubject()
{
    return subject;
}

public String[] getTo()
{
    return to;
}

}
    
class DocumentManagementSystem {

    public static void main(String[] args) {
    Document doc1=new Document();
    doc1.addAuthor("fathi");
    doc1.addAuthor("adnan");
    doc1.addAuthor("omar");
    
    System.out.println("authors list:");
    String a[]=doc1.getAuthors();
    for(int i=0;i<a.length;i++)
    System.out.println(a[i]);
    }
}

package com.mycompany.cis104;

import java.util.ArrayList;
import java.util.Scanner;

public class ArrayListClass {

    public static void main(String[] args) {

  Scanner input = new Scanner(System.in);
        System.out.print("Enter 3 numbers: ");
        ArrayList<Integer> list = new ArrayList<>();
        for (int i = 0; i < 3; i++) list.add(input.nextInt());

        System.out.println("Sorting numbers...");
        sort(list);
        System.out.println("Displaying numbers...");
        System.out.println(list);

        System.out.println("the summation of numbers in list is : "+sum(list));
    }

    public static void sort(ArrayList<Integer> list) {

        // simple solution
        //list.sort(null);

        // manual solution
        for (int i = 0; i < list.size() - 1; i++) {
            int currentMin = list.get(i);
            int currentIndex = i;

            for (int j = i + 1; j < list.size(); j++) {
                if (currentMin > list.get(j)) {
                    currentMin = list.get(j);
                    currentIndex = j;
                }
            }

            if (currentIndex != i) {
                list.set(currentIndex, list.get(i));
                list.set(i, currentMin);
            }
        }
    }
          public static Integer sum( ArrayList<Integer> list){

              Integer summation=0;
              for(Integer x:list)
              {
                  summation=summation+x;
              }
              return summation;
          }
}