What is a non-linear datastructure? A non-linear datastrucutre is a datastructure in which the data items in the memory are not allocated contiguously i.e. the data items are dispersed in the memory. The first data item will have a link to the second data item and second data item will have a link to the third data item and so on.

Pros
• Uses memory efficiently that the free contiguous memory in not an requirement for allocating data items
• The length of the data items is not necessary to be known prior to allocation
Cons
• Overhead of the link to the next data item Linked list: linked list a data structure which stores data in the form of nodes.It does not require linear memory as arrays. Each node contains a data part and a pointer part(a pointer to the next data in the list)

link or node is object of a class.there are so many types of linked list 1) single linked list
2)doubly linked list
3)circular linked list.

single linked list: here links contains pointer to first data and last data in the list.As said earlier a pointer to the next data. example of a linked list: class node{// all nodes will be the objects of this class public int data; public link next_node;//a pointer to next data
}
public node(int data){ this.data=data; }//end of constructor public void showdata(){
System.out.println("data= "+data);
}
}//end of class node

After defining class for each node we need to define a class for link list. Link list contains a pointer to the first node in the list,Which should be initialized to null in the beginning. All the operations to be performed on the link list is defined as functions in this class. For example insert first,Delete,insert search etc. class linkedlist{ private node first_node;//pointer to the first node is defined public linkedlist(){ first_node=null; } public void add_DAta(int data1){
//create newnode in the memory and store data node newnode= new node(data1);
//initially first data is null
//set the current first as the next node of the new node newnode.next_node=first; //set newnode as the first node first_node=newnode; }
}//end of class

Doubly link list:
This allows us to traverse backward and forward through the list . Here this a pointer to previous node i.e the class node in our example will have one more pointer to the previous node.
There is pointer to the last node in the list i.e class linkedlist contains pointer to last node in the list.
Circular linklist:
As the name indicate we can traversethe list i circular fashion that from first node to last node and back to firat node in the same direction. Last node will have a pointer to first node.