Merge pull request dubesar#541 from nimal96/master

added the doubly linked list

Author: dubesar

Data Structures/LinkedList/DoublyLinkedList.java

@@ -0,0 +1,113 @@
+/**
+ * A class that implements doubly linked list.
+ *
+ * @param <E> The type of the elements stored in the list
+ */
+public class DoublyLinkedList<E> {
+    private int size;
+    private ListNode<E> head;
+    private ListNode<E> tail;
+    public DoublyLinkedList(){
+        this.size = 0;
+        this.head = new ListNode<E>(null);
+        this.tail = new ListNode<E>(null);
+        this.head.setNext(this.tail);
+        this.tail.setPrev(this.head);
+    }
+
+    /*Implementing some List interface methods to get some idea*/
+
+    /**
+     * @return: returning DoublyLinkedList size
+     */
+    public int size() {
+        return this.size;
+    }
+
+    /**
+     * adding data to the end of the list
+     *
+     * @param data: data to be added into the end of list
+     */
+    public boolean add(E data){
+        ListNode<E> node = new ListNode<E>(data);
+        // adding the node at the end
+        node.setNext(this.tail);
+        node.setPrev(this.tail.getPrev());
+        this.tail.getPrev().setNext(node);
+        this.tail.setPrev(node);
+        size++;
+        return true;
+    }
+
+    /**
+     * get data from a specified index
+     * @param index
+     */
+    public E get(int index) {
+        int counter = 0;
+        ListNode<E> nodeCounter = this.head;
+        while(counter <= index){
+            nodeCounter = nodeCounter.getNext();
+            counter++;
+        }
+        return nodeCounter.getData();
+    }
+
+    /**
+     *
+     * @param index: index position where the node to add
+     * @param data: Data contained in that node
+     */
+    public boolean add(int index, E data){
+        ListNode<E> node = new ListNode<E>(data);
+        ListNode<E> nodeCounter = this.head;
+        int counter = 0;
+        while (counter <= index){
+            nodeCounter = nodeCounter.getNext();
+            counter++;
+        }
+        node.setNext(nodeCounter);
+        node.setPrev(nodeCounter.getPrev());
+        node.getPrev().setNext(node);
+        nodeCounter.setPrev(node);
+        return true;
+    }
+}
+
+/**
+ *
+ * @param <E> The type of element ListNode can have
+ */
+class ListNode<E>{
+    private ListNode<E> prev = null;
+    private ListNode<E> next = null;
+    private E data;
+    public ListNode(E theData){
+        this.data = theData;
+    }
+
+    public E getData() {
+        return data;
+    }
+
+    public ListNode<E> getNext() {
+        return next;
+    }
+
+    public ListNode<E> getPrev() {
+        return prev;
+    }
+
+    public void setData(E data) {
+        this.data = data;
+    }
+
+    public void setNext(ListNode<E> next) {
+        this.next = next;
+    }
+
+    public void setPrev(ListNode<E> prev) {
+        this.prev = prev;
+    }
+}