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Problem Solving Library for Java

There is a newer version: 0.1.19

package org.psjava.ds.deque;

import java.util.Iterator;

import org.psjava.ds.Collection;
import org.psjava.util.IterableToString;
import org.psjava.util.ReadOnlyIterator;

public class DoubleLinkedList implements Deque, Collection {

	public static  DoubleLinkedList create() {
		return new DoubleLinkedList();
	}

	private class Node {
		public T v;
		public Node n;
		public Node p;

		public Node(T v, Node p, Node n) {
			this.v = v;
			this.p = p;
			this.n = n;
		}
	}

	private final Node head;
	private final Node tail;

	public DoubleLinkedList() {
		head = new Node(null, null, null);
		tail = new Node(null, null, null);
		head.n = tail;
		tail.p = head;
	}

	@Override
	public void addToLast(T e) {
		add(tail, e);
	}

	@Override
	public void clear() {
		head.n = tail;
		tail.p = head;
	}

	@Override
	public boolean isEmpty() {
		return head.n == tail;
	}

	@Override
	public Iterator iterator() {
		return new ReadOnlyIterator() {
			Node next = head.n;

			@Override
			public boolean hasNext() {
				return next != tail;
			}

			@Override
			public T next() {
				T r = next.v;
				next = next.n;
				return r;
			}
		};
	}

	@Override
	public int size() {
		int r = 0;
		Node node = head;
		while (node.n != tail) {
			r++;
			node = node.n;
		}
		return r;
	}

	@Override
	public void addToFirst(T v) {
		add(head.n, v);
	}

	@Override
	public T getFirst() {
		return head.n.v;
	}

	@Override
	public T getLast() {
		return tail.p.v;
	}

	@Override
	public T removeFirst() {
		return remove(head.n);
	}

	@Override
	public T removeLast() {
		return remove(tail.p);
	}

	private T remove(Node node) {
		node.p.n = node.n;
		node.n.p = node.p;
		return node.v;
	}

	private void add(Node node, T v) {
		Node newNode = new Node(v, node.p, node);
		newNode.p.n = newNode;
		newNode.n.p = newNode;
	}

	@Override
	public String toString() {
		return IterableToString.toString(this);
	}

}