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);
+ }
+}