POSE3_06_Generics/src/ChainQueue.java

/************************************************
 * Name: David Wurm
 * Datum: 25.11.2019
 * Klasse: 3AHIF
 * Programm: HUE_06_GenericsQueue
 ************************************************/
import java.util.Collection;
import java.util.Iterator;
import java.util.Queue;

public class ChainQueue<E> implements Queue<E> {
    private class Node<E> {
        private E data;
        private Node<E> next;

        public Node<E> getNext() {
            return next;
        }

        public E getData() {
            return data;
        }

        public void setData(E data) {
            this.data = data;
        }

        public void setNext(Node<E> next) {
            this.next = next;
        }

        public Node(E data) {
            this.data = data;

        }
    }

    private Node<E> first; // first item of the queue

    public Node<E> getFirst() {
        return first;
    }

    public void setFirst(Node<E> first) {
        this.first = first;
    }

    @Override
    public boolean add(E input) {
        if (getFirst() == null) { // is the first empty?
            setFirst(new Node(input)); // yes? -> insert the node here
            return true;
        }
        return addNode(input, getFirst()); // no? -> goto addNode()
    }

    private boolean addNode(E input, Node n) { // run through the queue and find the first "place" which is empty
        if (n.getNext() == null) {
            n.setNext(new Node(input));
            return true;
        }
        return addNode(input, n.getNext());
    }

    @Override
    public int size() { // run through the queue and count the size
        Node temp = getFirst();
        int size = 0;
        while (temp != null) {
            size++;
            temp = temp.getNext();
        }
        return size;
    }


    @Override
    public boolean isEmpty() { // is the queue empty? -> size == 0
        if (this.size() == 0) {
            return true;
        }
        return false;
    }

    @Override
    public boolean contains(Object o) { // does object o exist in our queue?
        Node temp = getFirst();
        for (int i = 0; i < this.size(); i++) {
            if (getFirst().getData().equals(o)) {
                return true;
            }
            temp = temp.getNext();
        }
        return false;
    }

    @Override
    public E poll() { // poll next from queue and remove the first
        E temp = null;
        if (!this.isEmpty()) {
            temp = getFirst().getData();
            setFirst(getFirst().getNext());
        }
        return temp;
    }

    @Override
    public E element() {
        return null;
    }

    @Override
    public E peek() { // only "see" into the queue and do not remove anything
        if (!this.isEmpty()) {
            return getFirst().getData();
        }
        return null;
    }

    /*** the following is not implemented because it's not needed here ***/

    @Override
    public Iterator<E> iterator() {
        return null;
    }

    @Override
    public Object[] toArray() {
        return new Object[0];
    }

    @Override
    public <T> T[] toArray(T[] ts) {
        return null;
    }

    @Override
    public boolean remove(Object o) {
        return false;
    }

    @Override
    public boolean containsAll(Collection<?> collection) {
        return false;
    }

    @Override
    public boolean addAll(Collection<? extends E> collection) {
        return false;
    }

    @Override
    public boolean removeAll(Collection<?> collection) {
        return false;
    }

    @Override
    public boolean retainAll(Collection<?> collection) {
        return false;
    }

    @Override
    public void clear() {

    }

    @Override
    public boolean offer(E e) {
        return false;
    }

    @Override
    public E remove() {
        return null;
    }
}