Hacks Blog or illustrate understanding of the following.
- Watch the college board video Classes and Objects* Blog and Define the details of a Class: Access modifier, constructor, modifiers/setters, getters, etc.
- Build example code in jupyter notebook with Linked List, Queues, and Stacks.
- Show familiarity with managing data (aka nodes in LL) in these structures.
- Show familiarity with Generic data and ForEach loop support, similar to ArrayLists T. Here is sample Java Generic T and the Java Iterable interface by Geeks4Geeks.
/* This is wrapper class...
Objective would be to push more functionality into this Class to enforce consistent definition
*/
public abstract class Generics {
public final String masterType = "Generic";
private String type; // extender should define their data type
// generic enumerated interface
public interface KeyTypes {
String name();
}
protected abstract KeyTypes getKey(); // this method helps force usage of KeyTypes
// getter
public String getMasterType() {
return masterType;
}
// getter
public String getType() {
return type;
}
// setter
public void setType(String type) {
this.type = type;
}
// this method is used to establish key order
public abstract String toString();
// static print method used by extended classes
public static void print(Generics[] objs) {
// print 'Object' properties
System.out.println(objs.getClass() + " " + objs.length);
// print 'Generics' properties
if (objs.length > 0) {
Generics obj = objs[0]; // Look at properties of 1st element
System.out.println(
obj.getMasterType() + ": " +
obj.getType() +
" listed by " +
obj.getKey());
}
// print "Generics: Objects'
for(Object o : objs) // observe that type is Opaque
System.out.println(o);
System.out.println();
}
}
public class Alphabet extends Generics {
// Class data
public static KeyTypes key = KeyType.title; // static initializer
public static void setOrder(KeyTypes key) {Alphabet.key = key;}
public enum KeyType implements KeyTypes {title, letter}
private static final int size = 26; // constant used in data initialization
// Instance data
private final char letter;
/*
* single letter object
*/
public Alphabet(char letter)
{
this.setType("Alphabet");
this.letter = letter;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return Alphabet.key; }
/* 'Generics' requires toString override
* toString provides data based off of Static Key setting
*/
@Override
public String toString()
{
String output="";
if (KeyType.letter.equals(this.getKey())) {
output += this.letter;
} else {
output += super.getType() + ": " + this.letter;
}
return output;
}
// Test data initializer for upper case Alphabet
public static Alphabet[] alphabetData()
{
Alphabet[] alphabet = new Alphabet[Alphabet.size];
for (int i = 0; i < Alphabet.size; i++)
{
alphabet[i] = new Alphabet( (char)('A' + i) );
}
return alphabet;
}
/*
* main to test Animal class
*/
public static void main(String[] args)
{
// Inheritance Hierarchy
Alphabet[] objs = alphabetData();
// print with title
Alphabet.setOrder(KeyType.title);
Alphabet.print(objs);
// print letter only
Alphabet.setOrder(KeyType.letter);
Alphabet.print(objs);
}
}
Alphabet.main(null);
/*
* Animal class extends Generics and defines abstract methods
*/
public class Animal extends Generics {
// Class data
public static KeyTypes key = KeyType.title; // static initializer
public static void setOrder(KeyTypes key) { Animal.key = key; }
public enum KeyType implements KeyTypes {title, name, age, color}
// Instance data
private final String name;
private final int age;
private final String color;
/* constructor
*
*/
public Animal(String name, int age, String color)
{
super.setType("Animal");
this.name = name;
this.age = age;
this.color = color;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return Animal.key; }
/* 'Generics' requires toString override
* toString provides data based off of Static Key setting
*/
@Override
public String toString()
{
String output="";
if (KeyType.name.equals(this.getKey())) {
output += this.name;
} else if (KeyType.age.equals(this.getKey())) {
output += "00" + this.age;
output = output.substring(output.length() - 2);
} else if (KeyType.color.equals(this.getKey())) {
output += this.color;
} else {
output += super.getType() + ": " + this.name + ", " + this.color + ", " + this.age;
}
return output;
}
// Test data initializer
public static Animal[] animals() {
return new Animal[]{
new Animal("Lion", 8, "Gold"),
new Animal("Pig", 3, "Pink"),
new Animal("Robin", 7, "Red"),
new Animal("Cat", 10, "Black"),
new Animal("Kitty", 1, "Calico"),
new Animal("Dog", 14, "Brown")
};
}
/* main to test Animal class
*
*/
public static void main(String[] args)
{
// Inheritance Hierarchy
Animal[] objs = animals();
// print with title
Animal.setOrder(KeyType.title);
Animal.print(objs);
// print name only
Animal.setOrder(KeyType.name);
Animal.print(objs);
}
}
Animal.main(null);
public class Cupcake extends Generics {
// Class data
public static KeyTypes key = KeyType.title; // static initializer
public static void setOrder(KeyTypes key) {Cupcake.key = key;}
public enum KeyType implements KeyTypes {title, flavor, frosting, sprinkles}
// Instance data
private final String frosting;
private final int sprinkles;
private final String flavor;
// Constructor
Cupcake(String frosting, int sprinkles, String flavor)
{
this.setType("Cupcake");
this.frosting = frosting;
this.sprinkles = sprinkles;
this.flavor = flavor;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return Cupcake.key; }
/* 'Generics' requires toString override
* toString provides data based off of Static Key setting
*/
@Override
public String toString() {
String output="";
if (KeyType.flavor.equals(this.getKey())) {
output += this.flavor;
} else if (KeyType.frosting.equals(this.getKey())) {
output += this.frosting;
} else if (KeyType.sprinkles.equals(this.getKey())) {
output += "00" + this.sprinkles;
output = output.substring(output.length() - 2);
} else {
output = super.getType() + ": " + this.flavor + ", " + this.frosting + ", " + this.sprinkles;
}
return output;
}
// Test data initializer
public static Cupcake[] cupcakes() {
return new Cupcake[]{
new Cupcake("Red", 4, "Red Velvet"),
new Cupcake("Orange", 5, "Orange"),
new Cupcake("Yellow", 6, "Lemon"),
new Cupcake("Green", 7, "Apple"),
new Cupcake("Blue", 8, "Blueberry"),
new Cupcake("Purple", 9, "Blackberry"),
new Cupcake("Pink", 10, "Strawberry"),
new Cupcake("Tan", 11, "Vanilla"),
new Cupcake("Brown", 12, "Chocolate"),
};
}
public static void main(String[] args)
{
// Inheritance Hierarchy
Cupcake[] objs = cupcakes();
// print with title
Cupcake.setOrder(KeyType.title);
Cupcake.print(objs);
// print flavor only
Cupcake.setOrder(KeyType.flavor);
Cupcake.print(objs);
}
}
Cupcake.main(null);
/**
* Implementation of a Double Linked List; forward and backward links point to adjacent Nodes.
*
*/
public class LinkedList<T>
{
private T data;
private LinkedList<T> prevNode, nextNode;
/**
* Constructs a new element
*
* @param data, data of object
* @param node, previous node
*/
public LinkedList(T data, LinkedList<T> node)
{
this.setData(data);
this.setPrevNode(node);
this.setNextNode(null);
}
/**
* Clone an object,
*
* @param node object to clone
*/
public LinkedList(LinkedList<T> node)
{
this.setData(node.data);
this.setPrevNode(node.prevNode);
this.setNextNode(node.nextNode);
}
/**
* Setter for T data in DoubleLinkedNode object
*
* @param data, update data of object
*/
public void setData(T data)
{
this.data = data;
}
/**
* Returns T data for this element
*
* @return data associated with object
*/
public T getData()
{
return this.data;
}
/**
* Setter for prevNode in DoubleLinkedNode object
*
* @param node, prevNode to current Object
*/
public void setPrevNode(LinkedList<T> node)
{
this.prevNode = node;
}
/**
* Setter for nextNode in DoubleLinkedNode object
*
* @param node, nextNode to current Object
*/
public void setNextNode(LinkedList<T> node)
{
this.nextNode = node;
}
/**
* Returns reference to previous object in list
*
* @return the previous object in the list
*/
public LinkedList<T> getPrevious()
{
return this.prevNode;
}
/**
* Returns reference to next object in list
*
* @return the next object in the list
*/
public LinkedList<T> getNext()
{
return this.nextNode;
}
}
import java.util.Iterator;
/**
* Queue Iterator
*
* 1. "has a" current reference in Queue
* 2. supports iterable required methods for next that returns a generic T Object
*/
class QueueIterator<T> implements Iterator<T> {
LinkedList<T> current; // current element in iteration
// QueueIterator is pointed to the head of the list for iteration
public QueueIterator(LinkedList<T> head) {
current = head;
}
// hasNext informs if next element exists
public boolean hasNext() {
return current != null;
}
// next returns data object and advances to next position in queue
public T next() {
T data = current.getData();
current = current.getNext();
return data;
}
public LinkedList<T> getCurrent() {
return current;
}
}
/**
* Queue: custom implementation
* @author John Mortensen
*
* 1. Uses custom LinkedList of Generic type T
* 2. Implements Iterable
* 3. "has a" LinkedList for head and tail
*/
public class Queue<T> implements Iterable<T> {
LinkedList<T> head = null, tail = null;
/**
* Add a new object at the end of the Queue,
*
* @param data, is the data to be inserted in the Queue.
*/
public void add(T data) {
// add new object to end of Queue
LinkedList<T> tail = new LinkedList<>(data, null);
if (this.head == null) // initial condition
this.head = this.tail = tail;
else { // nodes in queue
this.tail.setNextNode(tail); // current tail points to new tail
this.tail = tail; // update tail
}
}
/**
* Returns the data of head.
*
* @return data, the dequeued data
*/
public T delete() {
T data = this.peek();
if (this.tail != null) { // initial condition
this.head = this.head.getNext(); // current tail points to new tail
if (this.head != null) {
this.head.setPrevNode(tail);
}
}
return data;
}
/**
* Returns the data of head.
*
* @return this.head.getData(), the head data in Queue.
*/
public T peek() {
return this.head.getData();
}
/**
* Returns the head object.
*
* @return this.head, the head object in Queue.
*/
public LinkedList<T> getHead() {
return this.head;
}
/**
* Returns the tail object.
*
* @return this.tail, the last object in Queue
*/
public LinkedList<T> getTail() {
return this.tail;
}
/**
* Returns the iterator object.
*
* @return this, instance of object
*/
public Iterator<T> iterator() {
return new QueueIterator<>(this.head);
}
/**
*
*/
public void printQueue() {
Iterator<T> iter = this.iterator();
String dataString = "";
int count = 0;
while(iter.hasNext()) {
dataString += iter.next() + " ";
count++;
}
System.out.println("Words count: " + count + ", data: " + dataString);
}
}
import java.util.Random;
/**
* Queue Manager
* 1. "has a" Queue
* 2. support management of Queue tasks (aka: titling, adding a list, printing)
*/
class QueueManager<T> {
// queue data
private final String name; // name of queue
private int count = 0; // number of objects in queue
public final Queue<T> queue = new Queue<>(); // queue object
/**
* Queue constructor
* Title with empty queue
*/
public QueueManager(String name) {
this.name = name;
}
/**
* Queue constructor
* Title with series of Arrays of Objects
*/
@SafeVarargs
public QueueManager(String name, T[]... seriesOfObjects) {
this.name = name;
this.addList(seriesOfObjects);
}
/**
* Add a list of objects to queue
*/
@SafeVarargs
public final void addList(T[]... seriesOfObjects) { //accepts multiple generic T lists
for (T[] objects: seriesOfObjects)
for (T data : objects) {
this.queue.add(data);
this.count++;
System.out.println("Enqueued data: " + data);
this.queue.printQueue();
}
}
/**
*
*/
public void deleteList() {
while(this.queue.getHead()!=null) {
T data = this.queue.delete();
System.out.println("Dequeued data: " + data);
this.queue.printQueue();
}
}
/**
* Print any array objects from queue
*/
public void printQueue() {
System.out.println(this.name + " count: " + count);
System.out.print(this.name + " data: ");
for (T data : queue)
System.out.print(data + " ");
System.out.println();
}
public static void mergeQueues(Queue<Integer> first, Queue<Integer> second) {
Queue<Integer> queue = new Queue<>();
Integer firstData = first.peek();
Integer secondData = second.peek();
while(firstData != null || secondData != null) {
if(firstData == null && secondData != null) {
queue.add(secondData);
second.delete();
if (second.getHead() == null) {
secondData = null;
} else {
secondData = second.peek();
}
}
if(firstData != null && secondData == null) {
queue.add(firstData);
first.delete();
if (first.getHead() == null) {
firstData = null;
} else {
firstData = first.peek();
}
}
if(firstData != null && secondData != null) {
if(firstData <= secondData) {
queue.add(firstData);
first.delete();
if (first.getHead() == null) {
firstData = null;
} else {
firstData = first.peek();
}
}
else {
queue.add(secondData);
second.delete();
if (second.getHead() == null) {
secondData = null;
} else {
secondData = second.peek();
}
}
}
}
queue.printQueue();
}
public void randomizeOrder() {
Random rand = new Random();
Object[] array = new Object[this.count];
Iterator<T> iter = this.queue.iterator();
int indexCount = 0;
while(iter.hasNext()) {
array[indexCount] = iter.next();
indexCount++;
}
for (int i = 0; i < array.length; i++) {
int index = rand.nextInt(i + 1);
Object g = array[index];
array[index] = array[i];
array[i] = g;
}
String printString = "";
for (int i = 0; i < array.length; i++) {
printString += array[i] + " ";
}
System.out.println("Randomized order: " + printString);
}
public void reverseQueue() {
Object[] stackArray = new Object[this.count];
Iterator<T> iter = this.queue.iterator();
int indexCount = this.count - 1;
// first item becomes last to come out, last in first out
while(iter.hasNext()) {
stackArray[indexCount] = iter.next();
indexCount--;
}
this.deleteList();
for (Object object: stackArray) {
@SuppressWarnings("unchecked")
T theObject = (T) object;
this.queue.add(theObject);
this.count++;
System.out.println("Enqueued data: " + object);
this.queue.printQueue();
}
}
}
/**
* Driver Class
* Tests queue with string, integers, and mixes of Classes and types
*/
class QueueTester {
public static void main(String[] args)
{
// Create iterable Queue of Words
Object[] words = new String[] { "seven", "slimy", "snakes", "sallying", "slowly", "slithered", "southward"};
QueueManager qWords = new QueueManager("Words", words );
qWords.deleteList();
qWords.printQueue();
}
}
QueueTester.main(null);
/**
* Driver Class
* Tests queue with string, integers, and mixes of Classes and types
*/
class QueueTester2 {
public static void main(String[] args)
{
Object[] numbers = new Integer[] { 1, 3, 4, 7};
QueueManager qNums = new QueueManager("Integers", numbers );
Object[] numbers2 = new Integer[] { 2, 5, 6, 8};
QueueManager qNums2 = new QueueManager("Integers", numbers2 );
Object[] numbers3 = new Integer[] { 1, 3, 4, 7};
QueueManager qNums3 = new QueueManager("Integers", numbers3 );
QueueManager.mergeQueues(qNums.queue, qNums2.queue);
qNums3.randomizeOrder();
}
}
QueueTester2.main(null);
/**
* Driver Class
* Tests queue with string, integers, and mixes of Classes and types
*/
class QueueTester3 {
public static void main(String[] args)
{
Object[] numbers3 = new Integer[] { 1, 3, 4, 7};
QueueManager qNums3 = new QueueManager("Integers", numbers3 );
qNums3.reverseQueue();
qNums3.printQueue();
}
}
QueueTester3.main(null);
/**
* Queue: custom implementation
* @author John Mortensen
*
* 1. Uses custom LinkedList of Generic type T
* 2. Implements Iterable
* 3. "has a" LinkedList for head and tail
*/
public class Stack<T> implements Iterable<T> {
LinkedList<T> head = null, tail = null;
/**
* Add a new object at the end of the Queue,
*
* @param data, is the data to be inserted in the Queue.
*/
public void add(T data) {
// add new object to end of Queue
LinkedList<T> head = new LinkedList<>(data, null);
if (this.head == null) // initial condition
this.head = this.tail = head;
else { // nodes in queue
this.head.setPrevNode(head); // current head points to new head
this.head = head; // update head
}
}
/**
* Returns the data of head.
*
* @return data, the dequeued data
*/
public T delete() {
T data = this.peek();
if (this.tail != null) { // initial condition
this.head = this.head.getNext(); // current tail points to new tail
if (this.head != null) {
this.head.setPrevNode(tail);
}
}
return data;
}
/**
* Returns the data of head.
*
* @return this.head.getData(), the head data in Queue.
*/
public T peek() {
return this.head.getData();
}
/**
* Returns the head object.
*
* @return this.head, the head object in Queue.
*/
public LinkedList<T> getHead() {
return this.head;
}
/**
* Returns the tail object.
*
* @return this.tail, the last object in Queue
*/
public LinkedList<T> getTail() {
return this.tail;
}
/**
* Returns the iterator object.
*
* @return this, instance of object
*/
public Iterator<T> iterator() {
return new QueueIterator<>(this.head);
}
/**
*
*/
public void printQueue() {
Iterator<T> iter = this.iterator();
String dataString = "";
int count = 0;
while(iter.hasNext()) {
dataString += iter.next() + " ";
count++;
}
System.out.println("Words count: " + count + ", data: " + dataString);
}
}