Generic Types Hacks
Queue<String> queue = new LinkedList<>(); // Queue interface uses LL implementation
queue.add("John");
queue.add("Jane");
queue.add("Bob");
// Collections has a toArray convertion
Object[] arr = queue.toArray();
// Empty queue
System.out.println("Empty Queue");
while (queue.size() > 0) // Interate while size
System.out.println(queue.remove());
// Iterate of array
System.out.println("Iterate over Array");
for (Object a : arr) // Type is Object from convertion
System.out.println(a);
/* 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);
public class Lingo extends Generics {
// Class data
public static KeyTypes key = KeyType.lang; // static initializer
public static void setOrder(KeyTypes key) {Lingo.key = key;}
public enum KeyType implements KeyTypes {lang, level, correct}
// Instance data
private final String lang;
private final String level;
private final int correct;
// Constructor
Lingo(String lang, String level, int correct)
{
this.setType("Lingo");
this.lang = lang;
this.level = level;
this.correct = correct;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return Lingo.key; }
/* 'Generics' requires toString override
* toString provides data based off of Static Key setting
*/
@Override
public String toString() {
String output="";
if (KeyType.lang.equals(this.getKey())) {
output += this.lang;
} else if (KeyType.level.equals(this.getKey())) {
output += this.level;
} else if (KeyType.correct.equals(this.getKey())) {
output += + this.correct;
} else {
output = super.getType() + ": " + this.lang + ", " + this.level + ", " + this.correct;
}
return output;
}
// Test data initializer
public static Lingo[] languages() {
return new Lingo[]{
new Lingo("Java", "Mastery", 9),
new Lingo("JavaScript", "Mastery", 10),
new Lingo("C#", "Beginner", 4),
new Lingo("Python", "Intermediate", 7),
};
}
public static void main(String[] args)
{
// Inheritance Hierarchy
Lingo[] objs = languages();
// print with language
Lingo.setOrder(KeyType.lang);
Lingo.print(objs);
// print level
Lingo.setOrder(KeyType.level);
Lingo.print(objs);
// print correct out of 10
Lingo.setOrder(KeyType.correct);
Lingo.print(objs);
}
}
Lingo.main(null);
CB video notes & definitions
- constructing an object using a class, and using an object
uses object.method because it is an accessor method that returns a variable that returns the method ex: String location = teacher.getLocation(); or teacher.changeLocation("Florida");
using static methods means that you can use the methods without creating an object, example being the Math class where you can say class.method instead of object.method
string class object where you can set it equal to a word like "theater" word.length
contructor is used to create the instance of the class
modifiers are used to change the access to a method, like public, private, etc
- setters/getters are used to protect the data in a class, getters return the value while setters sets or updates a value
/**
* 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;
}
}
/**
* 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);
}
}
/**
* 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
*/
public QueueManager(String name, T[]... seriesOfObjects) {
this.name = name;
this.addList(seriesOfObjects);
}
/**
* Add a list of objects to queue
*/
public void addList(T[]... seriesOfObjects) { //accepts multiple generic T lists
for (T[] objects: seriesOfObjects)
for (T data : objects) {
this.queue.add(data);
this.count++;
}
}
/**
* 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();
}
}
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.printQueue();
// Create iterable Queue of Integers
Object[] numbers = new Integer[] { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
QueueManager qNums = new QueueManager("Integers", numbers );
qNums.printQueue();
// Create iterable Queue of NCS Generics
Animal.setOrder(Animal.KeyType.name);
Alphabet.setOrder(Alphabet.KeyType.letter);
Cupcake.setOrder(Cupcake.KeyType.flavor);
// Illustrates use of a series of repeating arguments
QueueManager qGenerics = new QueueManager("My Generics",
Alphabet.alphabetData(),
Animal.animals(),
Cupcake.cupcakes()
);
qGenerics.printQueue();
// Create iterable Queue of Mixed types of data
QueueManager qMix = new QueueManager("Mixed");
qMix.queue.add("Start");
qMix.addList(
words,
numbers,
Alphabet.alphabetData(),
Animal.animals(),
Cupcake.cupcakes()
);
qMix.queue.add("End");
qMix.printQueue();
}
}
QueueTester.main(null);
// Hack 1
public class QueueExample {
public static void main(String[] args) {
Queue<String> queue = new LinkedList<String>();
// Adding elements to the queue
queue.add("seven");
System.out.println("Enqueued data: " + "seven");
printQueue(queue);
queue.add("slimy");
System.out.println("Enqueued data: " + "slimy");
printQueue(queue);
queue.add("snakes");
System.out.println("Enqueued data: " + "snakes");
printQueue(queue);
queue.add("sallying");
System.out.println("Enqueued data: " + "sallying");
printQueue(queue);
queue.add("slowly");
System.out.println("Enqueued data: " + "slowly");
printQueue(queue);
queue.add("slithered");
System.out.println("Enqueued data: " + "slithered");
printQueue(queue);
queue.add("southward");
System.out.println("Enqueued data: " + "southward");
printQueue(queue);
// Removing elements from the queue
String data =queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
data = queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
data = queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
data = queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
data = queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
data = queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
data = queue.remove();
System.out.println("Dequeued data: " + data);
printQueue(queue);
}
// Helper method to print the contents of the queue
public static void printQueue(Queue<String> queue) {
System.out.println("Words count: " + queue.size() + ", data: " + String.join(" ", queue));
System.out.println();
}
}
QueueExample.main(null);
//Hack 2 - merge 2 queues
Queue<Integer> questionNums1 = new LinkedList<>();
//offer adds an element to the end of the queue and
//returns a boolean value indicating whether the operation was successful
questionNums1.add(1);
questionNums1.add(4);
questionNums1.add(5);
questionNums1.add(8);
Queue<Integer> questionNums2 = new LinkedList<>();
questionNums2.add(2);
questionNums2.add(3);
questionNums2.add(6);
questionNums2.add(7);
Queue<Integer> mergedQueue = new LinkedList<>();
while (!questionNums1.isEmpty() && !questionNums2.isEmpty()) {
if (questionNums1.peek() < questionNums2.peek()) { //Retrieve the first element from each queue using the peek() method
//peek method returns the element at the front of the queue without removing it
mergedQueue.offer(questionNums1.poll());
} else { //Compare the two elements
//enqueue the smaller one to the new queue using the offer() method.
mergedQueue.offer(questionNums2.poll());
}//repeat
}
mergedQueue.addAll(questionNums1);
mergedQueue.addAll(questionNums2);
System.out.println("Python Question # Order: " + mergedQueue);
import java.util.Queue;
import java.util.LinkedList;
import java.util.Random;
public class ShuffleQueue {
public static void shuffle(Queue<String> queue) {
Random rand = new Random();
//static shuffle method that takes a Queue of strings as its argument and shuffles the elements
for (int i = 0; i < queue.size(); i++) {
int randomIndex = rand.nextInt(queue.size());
String temp = queue.peek();
//view or peek at the element at the front of the queue without removing it
for (int j = 0; j < randomIndex; j++) {
queue.add(queue.remove());
}//iterating through the queue and swapping
// each element with another element at a random position in the queue.
queue.remove();
for (int j = 0; j < randomIndex; j++) {
queue.add(queue.remove());
}
queue.add(temp);
}
}
//Random object to generate random indices within the size of the queue
//combination of remove and add methods to move elements around in the queue
public static void main(String[] args) {
Queue<String> queue = new LinkedList<>();
queue.add("Python");
queue.add("JavaScript");
queue.add("C#");
queue.add("Java");
System.out.println("Original queue: " + queue);
shuffle(queue);
System.out.println("Shuffled queue: " + queue);
}
}
ShuffleQueue.main(null);
//Hack 4
Queue<Integer> queue = new LinkedList<>();
//Create a new empty stack to store the elements of the queue
queue.offer(1);
queue.offer(2);
queue.offer(3);
queue.offer(4);
queue.offer(5);
Stack<Integer> stack = new Stack<>();
while (!queue.isEmpty()) {
stack.push(queue.poll());
}
//Dequeue all elements from the original queue and push them onto the stack
Queue<Integer> reversedQueue = new LinkedList<>();
while (!stack.isEmpty()) {
reversedQueue.offer(stack.pop());
}//Create a new empty queue to store the reversed elements
// pop removes and returns the top element of the stack
System.out.println("Original Question Numbers: " + queue);
System.out.println("Reversed Question Numbers: " + reversedQueue);
import java.util.Queue;
import java.util.Stack;
public class Languages {
public static void reverse(Queue<String> queue) {
Stack<String> stack = new Stack<>();
//The reverse method creates a new Stack object,
//then iterates through the elements in the queue, removing them one by one and pushing them onto the stack
while (!queue.isEmpty()) {
stack.push(queue.remove());
}
while (!stack.isEmpty()) {
queue.add(stack.pop()); //the method iterates
//through the elements in the stack, popping them off one by one and adding them back to the queue
}
}
}
System.out.println("Reversed queue of languages: "+queue);