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Thread: Traversing two different linked list

  1. #1
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    Default Traversing two different linked list

    I have a Product class that is the parent of 3 other classes; Books, Movies, Music. And the Product class connects to the Store class that holds the Store's location.

    If I need to find a certain Product I have to traverse the list of each the Store class and the Product class. However, my code is throwing a NullPointerExeption.

    When I debug it shows that pHead = null.

    I am thinking the error is within my addProductBook method and is not appointing the first product to head? Or my findProduct method holds the error.

    My constructor and addProductBook is in my Store Class
    	public Store() {
    		head = new Product(null, null, 0);
    	}
    		if(head == null) {
    			head = new Book(product, name, price, author, ISBN);
    			return;
    		}
    		else {
    			Book newBook = new Book(product, name, price, author, ISBN);
    			while(newBook.getNext() != null) {
    				newBook = (Book) newBook.getNext();
     
    				newBook.setNext(newBook);
    				Store.mainMenu();
    			}
    		}
    getProduct()
    returns product

    getName() - String
    returns name(Items name)

    findProduct is in a different Class
    	public static void findProduct(String item) {
    		Store current = head;
    		Product pHead = current.getProduct();
                    pHead.getName(); // This is a test spot that throws a NullPointerException
     
    		while(pHead != null && current != null){
    				if((pHead.getName().equals(item)))
    				pHead.printProduct();
     
    			else 
    				current.getNextStore();
    				pHead = pHead.getNext();
    				}
    Last edited by Usoda; March 10th, 2012 at 05:50 PM.


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