JAVA實現雙向鏈表

class DoubleLinkedList {

	public class Node {
		Object value;
		Node prev = this;
		Node next = this;

		public Node(Object v) {
			value = v;
		}

		public String toSting() {
			return value.toString();
		}
	}

	private Node head = new Node(null);// 頭節點
	private int size; // 鏈大小

	private Node getNode(int index) {
		if (index < 0 || index >= size) {
			throw new IndexOutOfBoundsException();
		}
		Node node = head.next;
		for (int i = 0; i < index; i++) {
			node = node.next;
		}
		return node;
	}

	private void addBefore(Node newNode, Node node) {
		newNode.prev = node.prev;
		newNode.next = node;
		newNode.next.prev = newNode;
		newNode.prev.next = newNode;
		size++;
	}

	private void addAfter(Node newNode, Node node) {
		newNode.prev = node;
		newNode.next = node.next;
		newNode.next.prev = newNode;
		newNode.prev.next = newNode;
		size++;
	}

	private void removeNode(Node node) {
		node.prev.next = node.next;
		node.next.prev = node.prev;
		node.prev = null;
		node.next = null;
		size--;
	}

	public boolean addFirst(Object o) {
		addAfter(new Node(o), head);
		return true;
	}

	public boolean addLast(Object o) {
		addBefore(new Node(o), head);
		return true;
	}

	public boolean add(int index, Object o) {
		addBefore(new Node(o), getNode(index));
		return true;
	}

	public Object get(int index) {
		return getNode(index).value;

	}

	public boolean remove(int index) {
		removeNode(getNode(index));
		return true;
	}

	public boolean removeFirst() {
		removeNode(head.next);
		return true;
	}

	public boolean removeLast() {
		removeNode(head.prev);
		return true;
	}

	public String toString() {
		StringBuffer s = new StringBuffer();
		Node node = head;
		for (int i = 0; i < size; i++) {
			node = node.next;
			s.append(",").append(node.value);
		}
		s.append("]");
		return "[" + s.substring(1);
	}
}

public class TestDoubleLinkedList {

	public static void main(String[] args) {
		DoubleLinkedList dll = new DoubleLinkedList();
		// 添加
		dll.addLast("1");
		dll.addLast("2");
		dll.addLast("3");
		dll.addLast("4");
		System.out.println(dll);
		dll.addFirst("5");
		System.out.println(dll);
		dll.addLast("6");
		System.out.println(dll);
		//移除
	    dll.removeFirst();
	    System.out.println(dll);
	    dll.removeLast();
	    System.out.println(dll);
	    dll.remove(2);
	    System.out.println(dll);
	    System.out.println(dll.get(1));
	}
}