An implementation of doubly linked list in java.

LinkedList.java

public class LinkedList {

  Node head;

	void insert(LinkedList li, Node x) {
		x.next = li.head;
		if (li.head != null) {
			li.head.pre = x;
		}
		li.head = x;
		x.pre = null;
	}

	Node search(LinkedList li, int key) {
		Node x = li.head;
		while (x != null && x.key != key) {
			x = x.next;
		}
		return x;
	}

	void delete(LinkedList l, Node x) {
		x = search(l, x);
		if (x.pre != null) {
			x.pre.next = x.next;
		} else {
			l.head = x.next;
		}
		if (x.next != null) {
			x.next.pre = x.pre;
		}
	}
}

class Node {
	Node pre;
	Node next;
	int key;

	Node(int key) {
		this.key = key;
	}
}