java 自定义双向链表

/**
 * 自定义双向链表
 *
 * @author 冯赵杨
 * @date 2018年4月10日
 */
public class DoubleLink<E> {
	private int n;
	private Node first;
	private Node last;

	private class Node {
		E value;
		Node next;
		Node prev;

		@Override
		public String toString() {
			return value + " ";
		}
	}

	/**
	 * 新增
	 *
	 * @author 冯赵杨
	 */
	public void add(E value) {
		Node oldlast = last;
		last = new Node();
		last.value = value;
		last.next = null;
		if (n == 0) {
			first = last;
		} else {
			oldlast.next = last;
			last.prev = oldlast;
			last.next = first;
			//System.out.println("last.value=" + last.value + ",last.prev=" + last.prev + ",last.next=" + last.next);
		}
		n++;
	}

	/**
	 * 反转
	 *
	 * @author 冯赵杨
	 */
	public DoubleLink<E> reverse(DoubleLink<E> link) {
		DoubleLink<E> newLink = new DoubleLink<E>();
		Node node = link.last;
		for (int i = 0; i < link.n; i++) {
			newLink.add(node.value);
			node = node.prev;
		}
		return newLink;
	}

	@Override
	public String toString() {
		StringBuilder str = new StringBuilder();
		Node node = first;
		for (int i = 0; i < n; i++) {
			str.append(node);
			node = node.next;
		}
		return str.toString();
	}


	public static void main(String[] args) {
		DoubleLink<Integer> doubleLink = new DoubleLink<Integer>();
		doubleLink.add(1);
		doubleLink.add(2);
		doubleLink.add(3);

		//原双向链表输出
		System.out.println(doubleLink.toString());

		//倒置后双向链表输出
		System.out.println(doubleLink.reverse(doubleLink));

	}

}