Double Link List .java

package com.demo.advjava;

public class DLList {

	Node head;

	class Node {
		int data;
		Node prev, next;

		public Node(int data) {
			this.data = data;
		}
	}

	public void pushAtFirst(int data) {
		Node newNode = new Node(data);

		newNode.prev = null;
		newNode.next = head;

		if (head != null) {
			head.prev = newNode;
		}

		head = newNode;
	}

	public void pushAfter(int data, int element) {
		Node newNode = new Node(data);
		Node previous, current;
		current = head;
		previous = head;
		while (current.data != element) {
			current = current.next;
			previous = current;
		}
		if (current.next != null) {
			current = current.next;
			previous.next = newNode;
			newNode.prev = previous;

			current.prev = newNode;
			newNode.next = current;
		} else {
			pushLast(data);
		}
	}

	public void pushBefore(int data, int element) {
		Node newNode = new Node(data);
		Node previous, current;
		current = head;
		previous = head;

		while (current.data != element) {
			current = current.next;
			previous = current;
		}

		if (previous.prev != null) {
			previous = current.prev;

			previous.next = newNode;
			newNode.prev = previous;

			current.prev = newNode;
			newNode.next = current;
		} else {
			pushAtFirst(data);
		}

	}

	public void pushLast(int data) {
		Node newNode = new Node(data);

		Node current = head;

		while (current.next != null) {
			current = current.next;
		}

		current.next = newNode;
		newNode.prev = current;
	}

	public void printAll(Node node) {
		while (node != null) {
			System.out.print(node.data + " ");
			node = node.next;
		}
	}

	public static void main(String[] args) {
		DLList dll = new DLList();
		dll.pushAtFirst(100);
		dll.pushAfter(400, 100);
		dll.pushLast(200);
		dll.pushAfter(300, 200);

		dll.pushBefore(23, 400);
		dll.pushBefore(24, 100);
		dll.pushBefore(245, 300);
		dll.printAll(dll.head);

	}
}