Implement the Iterator Pattern

Part II

Here is an implementation for hasNext and next methods:

public class ArrayIndexedListIterator<T> implements Iterator<T> {
  private T[] data;
  private int cursor;

  public ArrayIndexedListIterator(T[] data) {
    this.data = data;
    this.cursor = 0;
  }

  @Override
  public boolean hasNext() {
    return cursor < data.length;
  }

  @Override
  public T next() {
    if (!hasNext()) {
      throw new NoSuchElementException();
    }
    return data[cursor++];
  }
} 

Notes:

• We need to point to the data (elements) stored in the data structure we want to iterate over (the ArrayIndexedList here). Thus, we keep a reference (data) in the implementation provided here, which the constructor initializes.
• We use the cursor to keep track of the current element. The cursor is the index position of the current element. A "cursor" is not always as simple as an "index." Depending on the data structure, the "cursor" may require complex implementation.
• hasNext is true if the cursor has not reached the last element.
• next returns the current element pointed by the cursor and advances the cursor.
• next should throw NoSuchElementException when a client calls it after the iteration is over.

Now, update the implementation of ArrayIndexedList.iterator to use ArrayIndexedListIterator:

public class ArrayIndexedList<T> implements IndexedList<T> {

  // No changes were made to other operations.

  @Override
  public Iterator<T> iterator() {
    return new ArrayIndexedListIterator<>(this.data);
  } 
}

Run the tests and make sure they all pass!