java实现单双向链表

public class Node {
	private Object data;
	private Node next;

	public Node(Object data, Node next) {
		super();
		this.data = data;
		this.next = next;
	}

	public Object getData() {
		return data;
	}

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

	public Node getNext() {
		return next;
	}

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

public class LinkedList {
	private Node head;
	private Node tail;
	private int size;

	public void add(Object obj) {
		Node node = new Node(obj, null);
		if (head == null) {
			head = node;
			tail = node;
		}
		tail.setNext(node);
		tail = node;
		size++;
	}

	public int size() {
		return size;
	}
}

junit test code:
	@Test
	public void testAdd() {
		LinkedList linkedList = new LinkedList();
		for (int i = 0; i < 15; i++) {
			linkedList.add(new Cat(i));
		}
		assertTrue(linkedList.size()==15);
	}

public class LinkNode {
	private Object data;
	private LinkNode right;
	private LinkNode left;

	public LinkNode(Object data, LinkNode right, LinkNode left) {
		super();
		this.data = data;
		this.right = right;
		this.left = left;
	}

	public Object getData() {
		return data;
	}

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

	public LinkNode getRight() {
		return right;
	}

	public void setRight(LinkNode right) {
		this.right = right;
	}

	public LinkNode getLeft() {
		return left;
	}

	public void setLeft(LinkNode left) {
		this.left = left;
	}
}

public class Link {
	private LinkNode head;
	private LinkNode tail;
	private int size;

	public void add(Object obj) {
		LinkNode node = new LinkNode(obj, null, null);
		if (head == null) {
			head = node;
			tail = head;
			head.setRight(tail);
			head.setLeft(tail);
		}
		tail.setRight(node);
		node.setLeft(tail);
		tail = node;
		tail.setRight(head);
		head.setLeft(tail);
		size++;
	}

	public int size() {
		return size;
	}

	public LinkNode getTailNode() {
		return tail;
	}

	public LinkNode getHeadNode() {
		return head;
	}
}

junit test code:
	@Test
	public void testAdd() {
		Link link = new Link();
		for (int i = 0; i < 15; i++) {
			link.add(new Cat(i));
		}
		assertTrue(link.size()==15);
		
		assertEquals(link.getHeadNode().getLeft().getData(),link.getTailNode().getData());
		assertEquals(link.getTailNode().getRight().getData(),link.getHeadNode().getData());
	}