December 29, 2018

Create a Node class using java generic – for linked list

This class can not be used in any practical scenario. Because, the data part is going to be a lot different.

While learning the datastructures and algorithms, this class is going to be very useful. While working on any linked datastructures, we create a class which acts as a node. And, It has following fields.

  1. data :- It is the data, which is present in the node.
  2. next :- It is used to link the current node to the next node. It is used for keeping track of next node.
  3. prev :- It links the current node to previous node. It is used for keeping track of previous node.

We create a Node class with the following definition.

public class Node {                                                                                                                                                                                         
    public int data;                                                                                                                                                                                        
    public Node next;                                                                                                                                                                                       
    public Node prev;                                                                                                                                                                                       
    public Node(final int data) {                                                                                                                                         = data;                                                                                                                                                                              

But, the above definition has a problem. The above class  has data variable of int-type. If we need a data of string-type then we will have to create another class for it.

To solve this issue, we can use java-generics to create generic version of above class.

Like this

public class Node<T> {                                                                                                                                                                                      
    public T data;                                                                                                                                                                                          
    public Node next;                                                                                                                                                                                       
    public Node prev;                                                                                                                                                                                       
    public Node(final T data) {                                                                                                                                           = data;                                                                                                                                                                                

Now, we will have to mention the data-type while creating Node.

Like this.

Node<Integer> nodeInt = new Node<>(12);                                                                                                                                                 
Node<String> nodeString = new Node<>("Anurag");                                                                                                                                         
Node<Boolean> nodeBoolean = new Node<>(false);

Notice the use of diamond operator <> on the right side of equal= operator. This diamond operator is necessary, otherwise compiler will give you below warning.

Note: uses unchecked or unsafe operations.                                                                                                                                                        
Note: Recompile with -Xlint:unchecked for details.

Now, we can print data to check, it is working or not.