Collections
public abstract class Generics {
public final String masterType = "Generic"; // This string is used to indicate the type of the object
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 Group extends Generics {
// Class data
public static KeyTypes key = KeyType.title; // static initializer, sets order of elements which is set to title
public static void setOrder(KeyTypes key) {Group.key = key;}
public enum KeyType implements KeyTypes {title, name, grade, period}
// Instance data
private final String name;
private final int grade;
private final int period;
// Constructor
Group(String name, int grade, int period)
{
this.setType("Person");
this.name = name;
this.grade = grade;
this.period = period;
}
/* 'Generics' requires getKey to help enforce KeyTypes usage */
@Override
protected KeyTypes getKey() { return Group.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.grade.equals(this.getKey())) {
output += this.grade;
} else if (KeyType.period.equals(this.getKey())) {
output += this.period;
output = output.substring(output.length() - 2);
} else {
output = super.getType() + ": " + this.name + ", " + this.grade + ", " + this.period;
}
return output;
}
// Test data initializer
public static Group[] Group() {
return new Group[]{
new Group("Samuel", 12, 2),
new Group("Everitt", 12, 2),
new Group("Sahil", 12, 2),
};
}
public static void main(String[] args)
{
// Inheritance Hierarchy
Group[] objs = Group();
// print with title
Group.setOrder(KeyType.title);
Group.print(objs);
Group.setOrder(KeyType.name);
Group.print(objs);
}
}
Group.main(null);
public class LinkedList<T> // A doubly linked list is a data structure that consists of a sequence of nodes, where each node contains a value and two pointers, one to the previous node and one to the next node
{
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.*;
/**
* 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);
}
}
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 NCS Generics
Group.setOrder(Group.KeyType.name);
// Illustrates use of a series of repeating arguments
QueueManager qGenerics = new QueueManager("My Generics",Group.Group());
qGenerics.printQueue();
qGenerics.queue.add(new Group("Person", 99, 2));
qGenerics.printQueue();
}
}
QueueTester.main(null);
public static Queue shuffle(Queue q) {
Object[] arr = q.toArray(); // Convert queue to array
Random rand = new Random();
for (int i = arr.length - 1; i > 0; i--) {
int j = rand.nextInt(i + 1); // Pick a random index to swap with
Object temp = arr[i];
arr[i] = arr[j];
arr[j] = temp;
}
Queue shuffled = new Queue();
for (Object obj : arr) {
shuffled.add(obj); // Convert array back to queue
}
return shuffled;
}