This assignment allows a user to input names of birds. The program had to store that information in a linked list. The program also had to produce a count of the each bird population if the user requested it. As I came up against the dead, this assignment got a bit messy. It fully functions, of course, and met the requirements for the assignment.

BirdSurveyDemo.java

/*
Kurt Kaiser
CTIM 168
08.02.2018
Homework: Bird Survey Linked List
Chapter 12 Practice Problem 13
*/
import java.util.Scanner;

public class DemoSurvey {
    public static void main(String[] args) {
        HashMapBirdSurvey list = new HashMapBirdSurvey();
        boolean again = true;
        do {
            System.out.println("Inputs\n A to add birds\n C " +
                    "for a bird count\n R to print the report\n E to end");
            Scanner scan = new Scanner(System.in);
            String input = scan.nextLine();
            input.toLowerCase();
            switch (input) {
                case "a":
                    while (!input.equals("done")) {
                        list.addANodeToStart(input);
                        System.out.print("Bird name (done to exit): ");
                        scan = new Scanner(System.in);
                        input = scan.nextLine();
                    }
                    break;
                case "c":
                    System.out.print("Bird: ");
                    scan = new Scanner(System.in);
                    input = scan.nextLine();
                    list.getCount(input);
                    break;
                case "r":
                    list.getReport();
                    break;
                case "e":
                    again = false;
                    break;
            }
            System.out.println("");
        } while (again);
    }
}

HashMapBirdSurvey.java

/*
Kurt Kaiser
CTIM 168
08.02.2018
Homework: Bird Survey Linked List
Chapter 12 Practice Problem 13
*/

import java.util.HashMap;

public class HashMapBirdSurvey
{
    private ListNode head;

    public HashMapBirdSurvey() {
        head = null;
    }

    /**
     * Displays the data on the list.
     */
    public void showList() {
        ListNode position = head;
        while (position != null) {
            System.out.println(position.data);
            position = position.link;
        }

    }

    /**
     * Returns the number of nodes on the list.
     */
    public int length() {
        int count = 0;
        ListNode position = head;
        while (position != null) {
            count++;
            position = position.link;
        }
        return count;
    }

    /**
     * Adds a node containing the data addData at the
     * start of the list.
     */
    public void addANodeToStart(String addData) {
        head = new ListNode(addData, head);
    }

    /**
     * Deletes the first node on the list.
     */
    public void deleteHeadNode() {
        if (head != null)
            head = head.link;
        else {
            System.out.println("Deleting from an empty list.");
            System.exit(0);
        }
    }

    public void getReport() {
        ListNode position = head;
        position.createReport();
    }

    public void getCount(String bird) {
        ListNode position = head;
        position.searchBirdCount(bird);
    }


    /**
     * Sees whether target is on the list.
     */
    public boolean onList(String target) {
        return (find(target) != null);
    }

    //Returns a reference to the first node containing the
    //target data. If target is not on the list, returns null.
    private ListNode find(String target) {
        boolean found = false;
        ListNode position = head;
        while ((position != null) && !found) {
            String dataAtPosition = position.data;
            if (dataAtPosition.equals(target)){
                found = true;
            } else {
                position = position.link;
            }
        }
        return position;
    }

    private class ListNode {
        private String data;
        private ListNode link;
        private String[] array;
        private HashMap<String, Integer> countBirds;

        public ListNode() {
            link = null;
            data = null;
        }

        public ListNode(String newData, ListNode linkValue) {
            data = newData;
            link = linkValue;
        }


        public void toArray() {
            String[] anArray = new String[length()];
            ListNode position = head;
            int i = 0;
            while (position != null) {
                anArray[i] = position.data;
                i++;
                position = position.link;
            }
            array = anArray;
        }

        public void toHashMap() {
            countBirds = new HashMap<>();
            for (int j = 0; j < array.length; j++) {
                Integer count = countBirds.get(array[j]);
                if (count == null) {
                    count = 1;
                } else {
                    count++;
                }
                countBirds.put(array[j], count);
            }

        }

        public void searchBirdCount(String bird){
            toArray();
            toHashMap();
            Integer c = countBirds.get(bird);
            if (c == null) c = 0;
            System.out.println("Count: " + c);
        }

        public void createReport(){
            toArray();
            toHashMap();
            countBirds.forEach((key, value) -> System.out.println(key + ":" + value));
        }
    }

}