Hacks
Hacks
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 Language extends Generics {
// Class data
public static KeyTypes key = KeyType.language; // static initializer
public static void setOrder(KeyTypes key) {Language.key = key;}
public enum KeyType implements KeyTypes {model, language, type, year}
// Instance data
private final String language;
private final String type;
private final int year;
// Constructor
Language(String language, String type, int year)
{
this.setType("Language");
this.language = language;
this.type = type;
this.year = year;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return Language.key; }
/* 'Generics' requires toString override
* toString provides data based off of Static Key setting
*/
@Override
public String toString() {
String output="";
if (KeyType.language.equals(this.getKey())) {
output += this.language;
} else if (KeyType.type.equals(this.getKey())) {
output += this.type;
} else if (KeyType.year.equals(this.getKey())) {
output += "00" + this.year;
output = output.substring(output.length() - 2);
} else {
output = super.getType() + ": " + this.language + ", " + this.type + ", " + this.year;
}
return output;
}
// Test data initializer
public static Language[] Language() {
return new Language[]{
new Language("Java", "OO",1995),
new Language("HTML", "MarkUp",1999),
new Language("CSS", "Style",1996),
new Language("Markdown", "Markup",2004),
new Language("Javascript", "Frontend",1995),
new Language("Python", "OO",1991),
new Language("SQL", "Query",1970),
new Language("C++", "OO",1983),
};
}
public static void main(String[] args)
{
// Inheritance Hierarchy
Language[] objs = Language();
Language.setOrder(KeyType.model);
Language.print(objs);
// print with title
Language.setOrder(KeyType.language);
Language.print(objs);
}
}
Language.main(null);
public class language extends Generics {
// Class data
public static KeyTypes key = KeyType.title; // static initializer
public static void setOrder(KeyTypes key) { language.key = key; }
public enum KeyType implements KeyTypes {title, name, age, language}
// Instance data
private final String name;
private final int age;
private final String language;
/* constructor
*
*/
public language(String name, int age, String language)
{
super.setType("language");
this.name = name;
this.age = age;
this.language = language;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return language.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.language.equals(this.getKey())) {
output += this.language;
} else {
output += super.getType() + ": " + this.name + ", " + this.language + ", " + this.age;
}
return output;
}
// Test data initializer
public static language[] languages() {
return new language[]{
new language("Java", 6, "Object-Oriented"),
new language("Python", 2, "Object-Oriented"),
new language("HTML", 9, "HyperTextMarkup"),
new language("CSS", 5, "Style"),
new language("Javascript", 3, "Functional-f=Frontend"),
new language("Markdown", 1, "Markup")
};
}
/* main to test Animal class
*
*/
public static void main(String[] args)
{
// Inheritance Hierarchy
language[] objs = languages();
// print with title
language.setOrder(KeyType.title);
language.print(objs);
// print name only
language.setOrder(KeyType.name);
language.print(objs);
}
}
language.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;
}
}
/**
* 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();
}
}
import java.util.HashSet;
import java.util.Set;
public class AnimalSet {
public static void main(String[] args) {
// create a new HashSet
Set<String> animals = new HashSet<>();
// add some elements to the Set
animals.add("lion");
animals.add("dog");
animals.add("cat");
// print out the Set
System.out.println(animals);
// check if an element is in the Set
boolean hasLion = animals.contains("lion");
System.out.println("Has lion: " + hasLion);
// remove an element from the Set
animals.remove("lion");
System.out.println("Removed lion");
// print out the Set
System.out.println(animals);
// add duplicate
System.out.println("add duplicate dog");
animals.add("dog"); // no action
System.out.println(animals);
// add duplicate
System.out.println("add pig");
animals.add("pig");
System.out.println(animals);
// using forEach() method with a lambda expression
animals.forEach(animal -> {
String message = "I ";
message += animal.equals("dog") ? "like" : "don't like";
message += " " + animal + "s " + "for pets";
System.out.println(message);
});
}
}
AnimalSet.main(null);