Question

Need assistance with this problem. This is for a java class and using eclipse.

For this assignment we’ll be doing problems 21.3 and 21.4 from your textbook.

Problem 21.3 asks you to write a generic method that removes duplicate items from an ArrayList. This should be fairly straightforward. Problem 21.4 asks you to implement insertion sort within a generic method. Insertion sort is described in detail on pages 250-252 of your textbook.

You can write your two methods in a new class called Utilities. Please include a main method for this class that tests your methods.

Think carefully about the way you test your program. Developing a good test plan is as important as developing the code itself. Obviously, you should show that your generic methods work for different types of objects, i.e. ArrayLists or arrays of Integer, Strings, FacebookUsers,

etc. You should also test any unusual cases you can think of: what if the ArrayList or array is empty? what if it contains only one item? what if your removeDuplicates method is passed an ArrayList in which every item is identical? etc.

You will be graded according to the following rubric (each item is worth one point)

The removeDuplicates method works on at least some input

The removeDuplicates method is generic and therefore works on ArrayLists of all types of classes

The insertionSort method works on at least some input

The insertionSort method is generic and therefore works on ArrayLists of all types of classes that implement the Comparable interface

There is a main method that tests the operation of the removeDuplicates and insertionSort methods

The main method shows the operation of the removeDuplicates and insertionSort method on various types of classes, including FacebookUsers

The test cases in the main method are logical and thorough

The program compiles

The program runs

The program is clearly written and follows standard coding conventions

Answer 1

import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.Iterator;

public class Utilities {

        public static <T extends Comparable<T>> void insertionSort(ArrayList<T> numbers) {

                for (int i = 1; i < numbers.size(); i++) {
                        T key = numbers.get(i);
                        int j = i - 1;

                        while (j >= 0 && numbers.get(j).compareTo(key) > 0) {
                                numbers.set(j + 1, numbers.get(j));
                                j = j - 1;
                        }
                        numbers.set(j + 1, key);
                }
        }
        
        public static <T> void removeDuplicates(ArrayList<T> list) {
                HashSet<T> seen = new HashSet<>();
                
                Iterator<T> it = list.iterator();
                while(it.hasNext()) {
                        T next = it.next();
                        if(seen.contains(next)) {
                                it.remove();
                        } else {
                                seen.add(next);
                        }
                }
        }
        
        public static void main(String[] args) {
                ArrayList<Integer> nums = new ArrayList<>();
                
                nums.addAll(Arrays.asList(10, 20, 20, 6, 3, 14, 13, 23, 18, 13, 17, 13));
                System.out.println("Original list: " + Arrays.toString(nums.toArray()));

                Utilities.<Integer>removeDuplicates(nums);
                System.out.println("After removing duplicates: " + Arrays.toString(nums.toArray()));

                Utilities.<Integer>insertionSort(nums);
                System.out.println("After sorting: " + Arrays.toString(nums.toArray()));
                
        }

}

Please upvote, as i have given the exact answer as asked in question. Still in case of any issues in code, let me know in comments. Thanks!