Question

In your latest home assignment, you were asked to write a generic method that returns an ArrayList that contains the non-duplicate elements from the original list. For this question, write a generic method that returns an ArrayList that contains the non-duplicate elements or the duplicate elements depending on the boolean argument (dup) setting.

               If dup = false, return the list with the non-duplicates,

                 else return the list with the duplicated elements in the original list.

Please use the following two arrays for this question.

Integer[] nlist = { 0, 24, 25, 14, 25, 24, 42, 45, 42, 25};

String[] srt = {"Sam", "Bob", "Sue","Bob","Matt","Nick","Sue","Bob"};

Use the following static method (Array2Collection(….) to convert them to two corresponding ArrayLists ( 4 points)

public static <T> void Array2Collection(T a[], Collection<T> c) {

      for (T x: a)

            c.add(x);

}

Write codes to return an ArrayList <E>: if dup = false, return the list with the non-duplicates, else return with the duplicated element in the original list.

// 24 points­ for codes inside this method.

public static <E> ArrayList<E> Duplicates(ArrayList<E> list, boolean dup) {

// add codes here….

// 4 points for preparing the arrayList(s) from the two given arrays.

// 15 points for building the two arrayList of elements from the original list

// 5 points for returning the appropriate list based on the dup switch

}

Your client prgram should display this:

original list[0, 24, 25, 14, 25, 24, 14, 42, 45, 42, 25]

nodup list [0, 24, 25, 14, 42, 45]

dup list [25, 24, 14, 42, 25]

-------------

original list[Sam, Bob, Sue, Bob, Matt, Nick, Sue, Bob]

nodup list[Sam, Bob, Sue, Matt, Nick]

dup list[Bob, Sue, Bob]

Answer 1

Java Program:

import java.util.*;
class Main {
  public static <T> void Array2Collection(T a[], Collection<T> c)
  {
    for (T x: a)
      c.add(x);
  }

  public static <E> ArrayList<E> Duplicates(ArrayList<E> list, boolean dup)
  {
    ArrayList<E> d=new ArrayList<E>();
    if(dup)
    {
      HashMap<E,Integer> m=new HashMap<E,Integer>();
      for(E i:list)
      {
        m.put(i,m.getOrDefault(i,0)+1);
      }
      for(E i:list)
      {
        if(m.getOrDefault(i,0)>1)
        {
          if(m.getOrDefault(i,0)%2!=0)
          {
            d.add(i);
            m.put(i,m.getOrDefault(i,0)-1);
          }
          else
          {
            m.put(i,m.getOrDefault(i,0)+1);
          }
        }
      }
    }
    else
    {
      Set<E> s = new LinkedHashSet<E>(list);
      d=new ArrayList<E>(s);
    }
    return d;
  }
  public static void main(String[] args) {
    Integer[] nlist = { 0, 24, 25, 14, 25, 24,14, 42, 45, 42, 25};
    String[] srt = {"Sam", "Bob", "Sue","Bob","Matt","Nick","Sue","Bob"};
    ArrayList<Integer> li=new ArrayList<Integer>();
    Array2Collection(nlist,li);
    System.out.println("Original List "+li);
    System.out.println("Nodup List "+Duplicates(li,false));
    System.out.println("Dup List "+Duplicates(li,true));
    System.out.println("------------------------");
    ArrayList<String> ls=new ArrayList<String>();
    Array2Collection(srt,ls);
    System.out.println("Original List "+ls);
    System.out.println("Nodup List "+Duplicates(ls,false));
    System.out.println("Dup List "+Duplicates(ls,true));
  }
}

Output: