TheBoox(Idea)

Double linkedlist is used for dynamic memory allocation, there are several adivantages compares to Array
1) you can add elements in run time.
2) you have access to head and tail in O(1) time
3) you remove element from the list and you did not need to shift the element around like a Array.

Disadvantage compares to Array
1) you can’t access(index) any element in O(1) like an Array
2) harder to implement

how to remove node from double linked list?
we consider four cases:
1) if the link has only one node,
2) if the removed node is the head node and more than one node for the list
3) if the remove node is tail node and more than one node for the list
4) if the removed node is not a head or the tail node.
from the pic, we can see the four cases very easily.

full source code

import java.io.*;
import java.lang.String;

class Node
{
	Node prev;
	Node next;
	int data;
	public Node(int n)
	{ prev = next = null; data = n;}
}

class DLL
{
	Node head;
	Node tail;
	public DLL()
	{ head = tail = null;}
	public void append(Node no)
	{
		if(head == null)
		{ head = no; tail = head; }
		else
		{
			tail.next = no;
			no.prev = tail;;
			tail = tail.next;
		}
	}
	public void addfront(Node no)
	{
		if(head == null)
		{ head = no; tail = head;}
		else
		{
			head.prev = no;
			no.next = head;
			head = no;
		}
	}
	public void addNext(Node front, Node no)
	{
		if(front != null)
		{
			if(front.next == null)
			{ append(no);}
			else
			{
				Node cur = no;
				Node prev = front;
				Node next = front.next;

				cur.prev = prev;
				cur.next = next;
				prev.next = cur;
				next.prev = cur;
			}
		}
	}
	public void Remove(Node no)
	{
		if(no != null)
		{
			Node cur = head;
			while(cur != no) cur=cur.next;

			if(cur != null)
			{
				if(cur.prev == null)
				{
					System.out.println ("here1");
					if(cur.next != null)
					{
						Node prev = cur;
						cur = cur.next;
						head = cur;
						cur.prev = null;
						prev.next = null;
					}
					else
					{
						head = tail = null;
					}
				}
				else
				{
					System.out.println ("here2");
					if(cur.next != null)
					{
						Node prev = cur.prev;
						Node next = cur.next;
						prev.next = next;
						next.prev = prev;
						cur.next = null;
						cur.prev = null;
					}
					else
					{
						tail = cur.prev;
						tail.next = null;
						cur.prev = null;
					}
				}
			}
			else
				System.out.println("error");
		}
	}
	public void show()
	{
		Node cur = head;
		while(cur != null)
		{
			System.out.println ("cur=" + cur.data);
			cur = cur.next;
		}
	}
	public void show1()
	{
		Node cur = tail;
		while(cur != null)
		{
			System.out.println ("rev cur=" + cur.data);
			cur = cur.prev;
		}
	}

}

class Dlinkedlist
{
	public static void main(String args[])
	{
		DLL dll = new DLL();
		Node p1 = new Node(3);
		dll.append(p1);
		Node p2 = new Node(4);
		dll.append(p2);
		Node p3 = new Node(5);
		dll.append(p3);

		dll.addNext(p3, new Node(7));

		Node p4 = new Node(10);
		dll.append(p4);
		dll.show();
		dll.show1();

		dll.Remove(p4);
		System.out.println ("====");
		dll.show();
	}
}

how to remove node from Double Linked List