Doubly Link-List in Java

Doubly Link List

• As we can see here two nodes are connected among themselves with two links between them. 
• For first Node node0, next Node is node1 and node1 is connected with previous link between node0 and node1.
• Here first node is head and the last Node is tail. Both have value null and we same logic which we have in singly link list.  
/* ** Doubly Link List - Generic Class Shreyas Patel ** */ class Node<T> { public T Data; public Node Next; public Node Pre; public Node(){} public Node(T data) { Data = data; Next = Pre = null; } } class Doubly_Link<T> { private Node Head; private Node Tail; private int SIZE; public Doubly_Link() { Head = Tail = null; SIZE = 0; } public void Add_At_First(T data) { Node<T> n = new Node<T>(data); if(Head==null) { Head = n; Tail = Head; } else { Head.Pre = n; n.Next = Head; Head = n; } SIZE++; } public void Add_At_Last(T data) { Node<T> n=new Node<T>(data); if(Head==null) { Head=n; Tail=Head; } else { n.Pre=Tail; Tail.Next=n; Tail=n; } SIZE++; } public void Add_At_Position(T data,int Pos) { if(Pos==1)//Means first add { Add_At_First(data); return; } if(Pos==SIZE)//Means last add { Add_At_Last(data); return; } ////Else position add Node<T> n=new Node<T>(data); Node Dummy=null; if(Pos<=SIZE/2) { int count = 0; Dummy = Head; while(Dummy.Next!=null) { count++; if(count==Pos) {break;} else{Dummy=Dummy.Next;} } } else { int count = SIZE; Dummy = Tail; while(Dummy.Pre!=null) { if(count==Pos) {break;} else{Dummy=Dummy.Pre;} count--; } } Node Previous = Dummy.Pre; n.Pre = Previous; Previous.Next = n; Dummy.Pre = n; n.Next = Dummy; SIZE++; } public void Delete_From_First() { if(Head.Next==null) { Head=null;Tail=null; } else { Head=Head.Next; } SIZE--; } public void Delete_From_Last() { if(Tail.Pre==null) { Head=null;Tail=null; } else { Node Previous = Tail.Pre; Previous.Next = null; Tail = Previous; } SIZE--; } public void Delete_From_Position(int Pos) { if(Pos==1){Delete_From_First();return;} if(Pos==SIZE){Delete_From_Last();return;} Node Dummy=null; if(Pos<=SIZE/2) { int count = 0; Dummy = Head; while(Dummy.Next!=null) { count++; if(count==Pos) {break;} else{Dummy=Dummy.Next;} } } else { int count = SIZE; Dummy = Tail; while(Dummy.Pre!=null) { if(count==Pos) {break;} else{Dummy=Dummy.Pre;} count--; } } Node Previous = Dummy.Pre; Node UpNext = Dummy.Next; UpNext.Pre = Previous; Previous.Next = UpNext; SIZE--; } public void Display() { Node Dummy = Head; if(Head==null){System.out.println("\nNo data available.\n");return;} while(Dummy!=null) { System.out.println(Dummy.Data); Dummy = Dummy.Next; } } } ///Main Function class Doubly_LinkList { public static void main(String[] args) { System.out.println("\nNow for String.\n"); Doubly_Link<String> d= new Doubly_Link<String>(); d.Add_At_First("Shreyas"); d.Add_At_First("Kaksh"); d.Add_At_First("Mayuri"); d.Add_At_Last("Girishbhai"); d.Add_At_Position("Kiritbhai",3); d.Display(); //d.Delete_From_First(); //d.Delete_From_Last(); //d.Delete_From_Last(); //d.Delete_From_Last(); //d.Delete_From_Last(); //d.Delete_From_Last(); System.out.println("\nAt delete from position 3.\n"); d.Delete_From_Position(3); d.Display(); System.out.println("\nAt delete from position 1.\n"); d.Delete_From_Position(1); d.Display(); System.out.println("\nAt delete from position 2.\n"); d.Delete_From_Position(2); d.Display(); System.out.println("\nAt delete from position 1.\n"); d.Delete_From_Position(1); d.Display(); System.out.println("\nAt delete from position 1.\n"); d.Delete_From_Position(1); d.Display(); System.out.println("\nNow for Integer.\n"); Doubly_Link<Integer> i = new Doubly_Link<Integer>(); i.Add_At_First(4); i.Add_At_First(1); i.Add_At_First(8); i.Add_At_Last(2); i.Add_At_Position(7,3); i.Display(); System.out.println("\nAt delete from position 3.\n"); i.Delete_From_Position(3); i.Display(); System.out.println("\nAt delete from position 1.\n"); i.Delete_From_Position(1); i.Display(); System.out.println("\nAt delete from position 2.\n"); i.Delete_From_Position(2); i.Display(); System.out.println("\nAt delete from position 1.\n"); i.Delete_From_Position(1); i.Display(); System.out.println("\nAt delete from position 1.\n"); i.Delete_From_Position(1); i.Display(); } }