CODEWITHSUNDEEP
javaiterator
Saman Ray
Saman Ray

Reputation: 115

linkedlist add and remove not working as expected, Java

The following code is a Queue which is supposed to add and remove integer values but the function are not working as intended. Only first two values are added and remove function shows null pointer exception. In addition, the iterator class is not iterating over the Integer values. It causes infinite loop. What is the cause?

Thank you.

Upvotes: 0

Views: 84

Answers (1)

Hesham Attia
Hesham Attia

Reputation: 977

These two lines in the add method seem to be creating a cycle: 

front.next = previousNode;
previousNode.next = front;

The cycle here results in the infinite loop in iteration.

I think what you need is just to set the next of the previous node to the new node.

previousNode.next = front;

Also this part of the remove method doesn't seem correct:

E n = back.element;
back = back.next;
if (back == null)
    front = null;
else
    back.next = null;

The problem here is that you're setting back.next to null every time, which makes you lose the rest of the queue.

In order to fix that you just need to remove the else part, so that you keep the old next.

E n = back.element;
back = back.next;
if (back == null)
    front = null;

Upvotes: 1

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