Queue

import java.lang.reflect.Array;
import java.util.Iterator;

public class Queue<ELEMENT> implements Iterable<ELEMENT> {

    //region Constants

    protected final static Integer defaulDimension = 10;

    //endregion

    //region Attributes

    protected Class<?> elementClass;
    protected ELEMENT [] data;
    protected int head;
    protected int tail;
    protected int count;

    //endregion

    //region Constructors

    public Queue() {
        this(Queue.defaulDimension);
    }

    // from https://stackoverflow.com/questions/529085/how-to-create-a-generic-array-in-java
    @SuppressWarnings("unchecked")
    public Queue(int dimension, ELEMENT... dummy) {
        if (dummy.length > 0) {
            throw new IllegalArgumentException("No se debe facilitar valores para dummy");
        }
        elementClass = dummy.getClass().getComponentType();
        this.data = (ELEMENT []) Array.newInstance(this.elementClass, dimension);
        this.head = 0;
        this.tail = 0;
        this.count = 0;
    }
    //endregion

    //region Queue Internal Methods
    protected int next(int pos) {
        if (++pos >= this.data.length) {
            pos = 0;
        }
        return pos;
    }
    //endregion


    //region Queue Methods

    // Operacion EnQueue en la teoría de Estructura de Datos
    //
    // Inserts the specified element into this queue if it is possible to do so
    // immediately without violating capacity restrictions, returning true upon
    // success and throwing an IllegalStateException if no space is currently
    // available.
    public boolean add(ELEMENT element) {

        if (this.size() >= this.data.length) {
            throw new IllegalStateException("Cola llena ...");
        }

        this.data[this.tail] = element;
        this.tail = this.next(this.tail);
        ++this.count;

        return true;
    }

    // Operacion peek en la teoría de Estructura de Datos
    //
    // Retrieves, but does not remove, the head of this queue. This method differs
    // from peek only in that it throws an exception if this queue is empty.
    public ELEMENT element() {

        if (this.size() <= 0) {
            throw new IllegalStateException("Cola vacía ...");
        }

        return this.data[this.head];
    }

    // Operacion EnQueue en la teoría de Estructura de Datos
    //
    // Inserts the specified element into this queue if it is possible to do so
    // immediately without violating capacity restrictions. When using a
    // capacity-restricted queue, this method is generally preferable to add(E),
    // which can fail to insert an element only by throwing an exception.
    public boolean offer(ELEMENT element) {

        if (this.size() >= this.data.length) {
            return false;
        }

        this.data[this.tail] = element;
        this.tail = this.next(this.tail);
        ++this.count;

        return true;
    }

    // Retrieves, but does not remove, the head of this queue, or returns null if
    // this queue is empty.
    public ELEMENT peek() {
        if (this.size() <= 0) {
            return null;
        }

        return this.data[this.head];
    }

    // Operacion DeQueue en la teoría de Estructura de Datos
    //
    // Retrieves and removes the head of this queue, or returns null if this queue
    // is empty.
    public ELEMENT pool() {
        if (this.size() <= 0) {
            return null;
        }

        ELEMENT result = this.data[this.head];
        this.head = this.next(this.head);
        --this.count;

        return result;
    }

    // Operacion DeQueue en la teoría de Estructura de Datos
    //
    // Retrieves and removes the head of this queue. This method differs from poll()
    // only in that it throws an exception if this queue is empty.
    public ELEMENT remove() {
        if (this.size() <= 0) {
            throw new IllegalStateException("Cola vacía ...");
        }

        ELEMENT result = this.data[this.head];
        this.head = this.next(this.head);
        --this.count;

        return result;
    }
    //endregion


    //region Override Object basic methods

    @Override
    public String toString() {

        if (this.size() <=0) {
            return "";
        }

        // from https://docs.oracle.com/en/java/javase/15/docs/api/java.base/java/lang/StringBuilder.html
        StringBuilder sb = new StringBuilder();
        sb.append("[" + this.data[this.head].toString());

        for (int cta = 1, pos = this.next(this.head); cta < this.size(); ++cta, pos = this.next(pos)) {
            sb.append(", " + this.data[pos].toString());
        }

        sb.append("]");
        return sb.toString();
    }
    //endregion


    //region Collection Methods

    public boolean isEmpty() {
        return this.count <= 0;
    }

    public int size() {
        return this.count;
    }

    public ELEMENT[] toArray() {
        if (this.size() <= 0) {
            throw new IllegalStateException("Cola vacía ...");
        }

//        ELEMENT [] result = (ELEMENT []) new Object[this.size()];
        ELEMENT [] result = (ELEMENT []) Array.newInstance(this.elementClass, this.size());
        for(int i = 0, pos = this.head, cta = this.size(); cta > 0; ++i, pos = this.next(pos), --cta) {
            result[i] = this.data[pos];
        }
        return result;
    }
    //endregion


    //region Caso Ejemplo b) Methods

    public Queue<ELEMENT> union(Queue<ELEMENT> queue2) {
        return union(queue2, 0);
    }

    public Queue<ELEMENT> union(Queue<ELEMENT> queue2, int moreElements) {
        Queue<ELEMENT> queue1 = this;

        Queue<ELEMENT> result = new Queue<ELEMENT>(queue1.size() + queue2.size() + moreElements);

        for(int pos = queue1.head, cta = queue1.size(); cta > 0; pos = queue1.next(pos), --cta) {
            result.offer( queue1.data[pos] );
        }
        for(int pos = queue2.head, cta = queue2.size(); cta > 0; pos = queue2.next(pos), --cta) {
            result.offer( queue2.data[pos] );
        }

        return result;

    }
    //endregion


    //region Iterable Methods

    @Override
    public Iterator<ELEMENT> iterator() {
        return new QueueIterator(this);
    }

    private class QueueIterator implements Iterator<ELEMENT> {

        //region Attributes

        private Queue<ELEMENT> itQueue;
        private int itCount;
        private int itPos;

        //endregion

        //region Constructor

        public QueueIterator(Queue<ELEMENT> queue) {
            this.itQueue = queue;
            this.itCount = this.itQueue.size();
            this.itPos = this.itQueue.head;
        }

        //endregion

        @Override
        public boolean hasNext() {
            return this.itCount > 0;
        }

        @Override
        public ELEMENT next() {
            if ( !this.hasNext() ) {
                throw new RuntimeException("Error en el iterador de la cola...");
            }
            ELEMENT item = this.itQueue.data[this.itPos];
            this.itPos = this.itQueue.next(this.itPos);
            --this.itCount;
            return item;
        }
    }

    //endregion

    public boolean estaLlena(){
        if(this.count==this.data.length){
            System.out.println("la cola esta llena");
            return false;
        }
        return true;
    }
    public boolean estaVacia(){
        if (this.size() <= 0) {
            return true;
        }
        return false;
    }
    public int dimensiones(){
        int dim = this.data.length;
        return dim;

    }
}