Using ListIterator to move back and forth over a LinkedList in Java

Question

I have a LinkedList over which I need to iterate back and forth multiple times. I am using it to keep track of a series of pages in a workflow that will be created dynamically.

Answer 1

ListIterator was designed to behave this way. See the conversation beneath ShyJ's answer for the rationale.

I find this behavior to be beyond idiotic, and have instead written a very simple alternative. Here's the Kotlin code with a extension function for ArrayLists:

class ListIterator(var list: ArrayList) : Iterator {

    private var cursor: Int = 0

    fun replace(newList: ArrayList) {
        list = newList
        cursor = 0
    }

    override fun hasNext(): Boolean {
        return cursor + 1 < list.size
    }

    override fun next(): E {
        cursor++
        return current()
    }

    fun hasPrevious(): Boolean {
        return 0 <= cursor - 1
    }

    fun previous(): E {
        cursor--
        return current()
    }

    fun current(): E {
        return list[cursor]
    }

}

fun  ArrayList.listFlippingIterator() = ListIterator(this)

If you wish to include removal functionality, I highly recommend writing the API to explicitly instruct the iterator if it should remove left or right, e.g. by defining those methods as removeNext() and removePrevious().