DoublyLinkedList.java

package Test;


/*
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 */
import java.util.*;
/**
 *
 * @author asraf
 */
public class DoublyLinkedList<E>{  
    
    public class PostNode<E>{
    E post;
    PostNode<E> next;
    PostNode<E> prev;
    
    public PostNode(E post, PostNode next, PostNode prev){
        this.post = post;
        this.next = next;
        this.prev = prev;
    }
    
    public PostNode(E post){
        this(post, null, null);
    }
}
    PostNode<E> head;
    private PostNode<E> tail;
    PostNode<E> iterate;                                                        //Used when iterating in DoublyLinkedList, Tester2 class
    private int size;
    
    public DoublyLinkedList(){
        size = 0;
        this.head = null;
        this.tail = null;
    }
    
    public int Size(){
        return size;
    }
    
    public boolean isEmpty(){
        return size == 0;
    }
    
    public void addFirst(E element) {
        //create object tmp and set pointer of the new node
        PostNode<E> tmp = new PostNode(element, head, null);
        //set head.prev of current head to be linked to the new node
        if(head != null ) {head.prev = tmp;} 
        head = tmp; //now tmp become head
        iterate = head;
        //if no tail, then tmp set to be a tail
        if(tail == null) { tail = tmp;}
        size++;//increase number of node
    }
     
    
    public void add(E element) {        //implementing addLast method
        //create object tmp and set pointer of the previous node
        PostNode<E> tmp = new PostNode(element, null, tail);
        //set tail.next point to object tmp
        if(tail != null) {tail.next = tmp;}
        //now tmp become tail
        tail = tmp;
        //if no head, then tmp set to be a head
        if(head == null) { head = tmp; iterate=head;}
        size++;//increase number of node
    }
     
    
//    public void iterateForward(){
//         
//        System.out.println("iterating forward..");
//        PostNode<E> tmp = head;
//        while(tmp != null){
//            System.out.print(tmp.post);
//              System.out.print(" ");
//            tmp = tmp.next;
//        }
//    }
     
   
//    public void iterateBackward(){
//         
//        System.out.println("iterating backward..");
//        PostNode<E> tmp = tail;
//        while(tmp != null){
//            System.out.println(tmp.post);
//            tmp = tmp.prev;
//        }
//    }
    
//    public E next() {
//        if (current != null){
//        E tmp = (E) current.post;
//        current = current.next; 
//        return tmp;
//        }else{
//        return null;
//        }
//    }
    
    public E removeFirst() {
        if (size == 0) throw new NoSuchElementException();
       //copy head to node tmp
        PostNode<E> tmp = head;
        //head.next become a head
        head = head.next;
        //set pointer of prev of new head to be null
        head.prev = null;
        //reduce number of node
        size--;
        return tmp.post;
    }
     
    
    public E removeLast() {
        if (size == 0) throw new NoSuchElementException();
         //copy tail to node tmp
        PostNode<E> tmp = tail;
        //tail.prev become a tail
        tail = tail.prev;
        //set pointer of next of new tail to be null
        tail.next = null;
       //reduce number of node
        size--;
        return  tmp.post;
    }
     
    public void add(int index, E element){
		//index can only be 0 ~ size()
		if(index < 0 || index > size)
			throw new IndexOutOfBoundsException();
		if(index == 0)
			addFirst(element);
		else if(index == size)
			add(element);
		else{
                        /* set from head and begin traverse
                        stop on required position */
			PostNode<E> temp = head;
			for(int i=0; i<index; i++){
				temp = temp.next;
			}
                        /* create object insert and set pointer of the next pointer
                        to the temp node and also set pointer of the prev pointer
                        to the temp.prev node
                        */
			PostNode<E> insert = new PostNode(element, temp, temp.prev);
			//set pointer 'next' of the node temp.prev to new node insert
                        temp.prev.next = insert;
			//set pointer 'prev' of the node temp to new node insert
                        temp.prev = insert;
			size ++;
		}
	}   //might not be used
    
   public E remove(int index){
		E element = null;
		if(index < 0 || index >=size)
			throw new IndexOutOfBoundsException();
		if(index == 0)
			element=removeFirst();
		else if(index == size-1)
			element=removeLast();
		else{
			PostNode<E> temp = head;
			for(int i=0; i<index; i++){
				temp = temp.next;
			}
			element = temp.post;
			temp.next.prev = temp.prev;
			temp.prev.next = temp.next;
			temp.next = null;
			temp.prev = null;
			size --;
		}
		return element;
   }
    
    public void clear(){
		PostNode<E> temp = head;
		while(temp != null){
			temp = head.next;
			temp.prev = temp.next = null;
			head = temp;
		}
		head = null;
		tail = null;
		size = 0;
	}
    
    /**
     * Returns the current post in the iteration.
     * @return  current Confession Post data in the iteration
     */
    public E returnCurrentPost() {
//        try{
        if(iterate != null){
            return iterate.post;
        }
//        }catch (NullPointerException e){
//            System.out.println("End of List...");
//        }
            return null;
    }
    
    /**
     * Sets iterate value as the first Confession Post in the iteration.
     */
    public void firstPost(){
        iterate = head;
    }
    
    /**
     * Sets iterate value as the last Confession Post in the iteration.
     */
    public void lastPost(){
        iterate = tail;
    }
    
    /**
     * Sets iterate value as the next Confession Post in the iteration.
     */
    public void nextPost(){
        if(iterate != null){
            iterate = iterate.next;
        }
    }
    
    /**
     * Sets iterate value as the previous Confession Post in the iteration.
     */
    public void previousPost(){
        if(iterate != null){
            iterate = iterate.prev;
        }
    }
}