implement addAtIndex() to add element at any index

in the list.

Author: rajendrapancholi

DoublyLinkedList.java

@@ -3,67 +3,119 @@ private static class Node<E> {
         private E element;
         private Node<E> prev;
         private Node<E> next;
-        public Node(E e, Node<E> p, Node<E> n){
+
+        public Node(E e, Node<E> p, Node<E> n) {
             element = e;
             prev = p;
             next = n;
         }
-        public E getElement() { return element; }
-        public Node<E> getPrev() { return prev; }
-        public Node<E> getNext() { return next; }
-        public void setPrev(Node<E> p) { prev = p;}
-        public void setNext(Node<E> n) { next = n;}
+
+        public E getElement() {
+            return element;
+        }
+
+        public Node<E> getPrev() {
+            return prev;
+        }
+
+        public Node<E> getNext() {
+            return next;
+        }
+
+        public void setPrev(Node<E> p) {
+            prev = p;
+        }
+
+        public void setNext(Node<E> n) {
+            next = n;
+        }
     }
+
     private Node<E> header;
     private Node<E> tailer;
     private int size = 0;
-    //constructor a new empty list
-    public DoublyLL(){
+
+    // constructor a new empty list
+    public DoublyLL() {
         header = new Node<>(null, null, null);
         tailer = new Node<>(null, header, null);
         header.setNext(tailer);
     }
-    public int size(){
+
+    public int size() {
         return size;
     }
-    public boolean isEmpty(){
+
+    public boolean isEmpty() {
         return size == 0;
     }
-    public E first(){
+
+    public E first() {
         if (isEmpty()) {
             return null;
         }
         return header.getNext().getElement();
     }
-    public E last(){
+
+    public E last() {
         if (isEmpty()) {
             return null;
         }
         return tailer.getPrev().getElement();
     }
-    //update methods
-    public void addFirst(E e){
+
+    // update methods
+    public void addFirst(E e) {
         addBetween(e, header, header.getNext());
     }
-    public void addLast(E e){
+
+    public void addLast(E e) {
         addBetween(e, tailer.getPrev(), tailer);
     }
-    public E removeFirst(){
+
+    public void addAtIndex(E e, int index) {
+        if (index < 0 || index > size) {
+            throw new IndexOutOfBoundsException("Index: " + index + " size: " + size);
+        }
+        if (isEmpty()) {
+            addBetween(e, tailer, header.getNext());
+        } else if (index == 0) {
+            addBetween(e, header, header.getNext());
+        } else if (index == size) {
+            addBetween(e, tailer.getPrev(), tailer);
+        }
+
+        else {
+            Node<E> newNode = header;
+            for (int i = 0; i < index; i++) {
+                System.out.println("\nelemet at: " + i + " e: " + newNode.getElement());
+                newNode = newNode.getNext();
+            }
+            addBetween(e, newNode, newNode.getNext());
+            System.out.println("\nheader: " + newNode.getElement());
+        }
+    }
+
+    public E removeFirst() {
         if (isEmpty()) {
             return null;
         }
         return remove(header.getNext());
     }
-    public E removeLast(){
-        if (isEmpty()) return null;
+
+    public E removeLast() {
+        if (isEmpty())
+            return null;
         return remove(tailer.getPrev());
     }
-    private void addBetween(E e, Node<E> predecessor, Node<E> successor ){
+
+    private void addBetween(E e, Node<E> predecessor, Node<E> successor) {
         Node<E> newest = new Node<>(e, predecessor, successor);
         predecessor.setNext(newest);
         successor.setPrev(newest);
         size++;
     }
+
     private E remove(Node<E> node) {
         Node<E> predecessor = node.getPrev();
         Node<E> successor = node.getNext();
@@ -72,33 +124,39 @@ private E remove(Node<E> node) {
         size--;
         return node.getElement();
     }
-    public void display(){
+
+    public void display() {
         if (isEmpty()) {
             System.out.println("List is empty!");
             return;
         }
         Node<E> current = header.getNext();
-        while(current != null){
-            System.out.print(current.getElement()+ " ");
+        while (current != null) {
+            System.out.print(current.getElement() + " ");
             current = current.getNext();
-            if (current.getElement() ==null) {
+            if (current.getElement() == null) {
                 return;
             }
         }
     }
 
 }
-public class DoublyLinkedList{
-    public static void main(String[] args){
+
+public class DoublyLinkedList {
+    public static void main(String[] args) {
         DoublyLL<Integer> dll = new DoublyLL<>();
         dll.addFirst(3);
         dll.addFirst(2);
         dll.addFirst(1);
         dll.addLast(4);
-        System.out.println("First element: "+dll.first());
-        System.out.println("Last element: "+dll.last());
-        System.out.println("Total element: "+dll.size());
+        // dll.addAtIndex(33, 3);
+        System.out.println("First element: " + dll.first());
+        System.out.println("Last element: " + dll.last());
+        System.out.println("Total element: " + dll.size());
         System.out.println("Doubly Linked List: ");
         dll.display();
+        dll.addAtIndex(13, 3);
+        System.out.println("\nAfter inserting at i");
+        dll.display();
     }
 }

Hello.java

@@ -0,0 +1,11 @@
+
+public class Hello {
+    public static int myvar = 45;
+    public static int var = 5;
+
+    public static void main(String[] args) {
+        System.out.println("this is rajendra pancholi" + myvar);
+        System.err.println("Error");
+
+    }
+}

HelloWorldGUI1.java

@@ -0,0 +1,6 @@
+import javax.swing.JOptionPane;
+public class HelloWorldGUI1 {
+    public static void main(String[] args) {
+        JOptionPane.showMessageDialog( null, "Hello Rajendra Pancholi!" );
+    }
+}

HelloWorldGUI2.java

@@ -0,0 +1,31 @@
+import java.awt.*;
+import java.awt.event.*;
+import javax.swing.*;
+public class HelloWorldGUI2 {
+    private static class HelloWorldDisplay extends JPanel {
+        public void paintComponent(Graphics g) {
+            super.paintComponent(g);
+            g.drawString( "Hello Rajendra Pacholi!", 20, 30 );
+        }
+    }
+    private static class ButtonHandler implements ActionListener {
+        public void actionPerformed(ActionEvent e) {
+            System.exit(0);
+        }
+    }
+    public static void main(String[] args) {
+        HelloWorldDisplay displayPanel = new HelloWorldDisplay();
+        JButton okButton = new JButton("OK");
+        ButtonHandler listener = new ButtonHandler();
+        okButton.addActionListener(listener);
+        JPanel content = new JPanel();
+        content.setLayout(new BorderLayout());
+        content.add(displayPanel, BorderLayout.CENTER);
+        content.add(okButton, BorderLayout.SOUTH);
+        JFrame window = new JFrame("Raje");
+        window.setContentPane(content);
+        window.setSize(250,200);
+        window.setLocation(400,100);
+        window.setVisible(true);
+    }
+}