CODEWITHSUNDEEP
javalinked-listlistiterator
randomuser1
randomuser1

Reputation: 2803

how can I get the next object on my linkedlist?

I have a LinkedList of objects in Java and I want to iterate through it, and when I find a specific object there - I want to take the next object (the one that is right next to the first one).

I thought this would solve the case:

listIterator = items.listIterator();
while (listIterator.hasNext() && listIterator.previous().getCode().equals(search.getCurrentCode())) {

    item = listIterator.next();
    result.setCurrentCode(item.getCode());
    break;
}

but I'm getting error:

java.util.NoSuchElementException: null

I think it's because of using .previous, but I don't know how to handle that correctly, how could I solve it then? I'm using previous, but what I want is to use the current element - I thought that's handled by .previous, but apparently it's not.

Upvotes: 0

Views: 230

Answers (3)

Ousmane D.
Ousmane D.

Reputation: 56433

First, I'd suggest using an ArrayList instead of LinkedList as the former is almost always the better option to use. see this post for more information.

You could definitely do this via a typical for loop or enhanced for loop, but I'd like to illustrate a new method as of JDK9 called dropWhile which can help you accomplish this requirement of yours:

Assuming, you have your ArrayList in place. you could simply do:

myList.stream()
      .dropWhile(c -> !c.getCode().equals(search.getCurrentCode()))
      .skip(1) // get the object to the right of the matched item
      .findFirst() // retrieve this object
      .ifPresent(s -> result.setCurrentCode(s.getCode())); // apply the logic based on the found object

Upvotes: 0

Eugen
Eugen

Reputation: 917

Try this:

listIterator = items.listIterator();
// listIterator.previous() does not exist in first iteration
while (listIterator.hasNext()) {
// you can compare previous value if it exist
if(listIterator.hasPrevious() && listIterator.previous().getCode().equals(search.getCurrentCode())){
    item = listIterator.next();
    result.setCurrentCode(item.getCode());
    break;
}
}

Upvotes: 0

miskender
miskender

Reputation: 7958

Your current code fails because You are calling previous, before even start iterating on items. Iteration is done with listIterator.next(); call. You can try the code below.

while (listIterator.hasNext()){
   // iterate always
   item = listIterator.next();
   // if found and an element still exist
   if(item.getCode().equals(search.getCurrentCode() && listIterator.hasNext()){
      // get the next element
      item = listIterator.next();
      result.setCurrentCode(item.getCode());
      break;
   }
}

Upvotes: 2

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