CODEWITHSUNDEEP
javaiterable
pedron
pedron

Reputation: 237

Java Iterable object won't Iterate correctly

I have a java object that implements the Iterable interface. This linked list has a group of objects that each hold a parameterized object (so it could be a String OR an ArrayList or whatever).

In the iterator() method, i create an Iterator object that takes an array of these parameterized items and return it.

However, when i use the following code:

//create an Iterable object named 'iterate'
for(String current : iterate){
//try to do some stuff with it... print it out?
}

//more code

//here is how i implemented the iterator function of my Iterable class:

public Iterator<Item> iterator(){
   // return an iterator over items in order from front to end
    Item[] items = (Item[]) new Object[numberOfItems];
    QueueItem<Item> item = first;
    for(int i=0;i<numberOfItems;i++){
        items[i] = item.getInfo();
        item = item.next;
    }
    return new myIterator(items);
}

//here is the code for the myIterator class. it is a private internal class

private class myIterator implements Iterator<Item>{

    Item items[];
    int index;
    public myIterator(Item current[]){
        items = current;
        index = 0;
    }
    @Override
    public boolean hasNext() {
        if(items==null){
            return false;
        }
        return (index>=items.length);
    }

    @Override
    public Item next() {
        if(index+1>=items.length){
            throw new NoSuchElementException("There are no more elements!");
        }
        return items[index++];
    }

    @Override
    public void remove() {
        throw new UnsupportedOperationException("this operation is not supported");
    }

}

the code goes to the for loop, then creates the Iterator object correctly (I used breakpoints to confirm), and returns it, but then the code jumps out of the for loop without going through it even once and continues....

Am i missing something? did i do something wrong here? how do i need to change the implementation of my Iterable object? is there some GOTCHA with implementing this that i'm not taking into account?

thanks!

Upvotes: 0

Views: 171

Answers (2)

pedron
pedron

Reputation: 237

oh my gosh. so embarrassing. the hasNext method had the boolean statement reversed.

it should have been: 

return (index<items.length); thanks anyways!

i've been pulling my hair out about this. i debugged everything else, then it dawned on me.

This is my first iterator implementation, so i figured it must have been something more fundamental that i wasn't doing correctly.

Upvotes: 0

Tomas Bisciak
Tomas Bisciak

Reputation: 2841

in hasNext method you check if return (index>=items.length); Well this will return false. change operant to "<"

Upvotes: 2

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