Iterator Implementation

Question

I had to write my own iterator implementation for my structure which has ArrayList<Vector> field. An iterator is supposed to iterate over mentioned List. Any suggestions on improving it, or anything else?

public class ExamplesIterator implements Iterator<Vector> {
 private List<Vector> examples; //ArrayList<Vector> will be set here
 private int index;
 public ExamplesIterator(List<Vector> examples) {
 this.examples = examples;
 index = 0;
 }
 @Override
 public Vector next() {
 if(hasNext()) {
 return examples.get(index++);
 } else {
 throw new NoSuchElementException("There are no elements size = " + examples.size());
 }
 }
 @Override
 public boolean hasNext() {
 return !(examples.size() == index);
 }
 @Override
 public void remove() {
 if(index <= 0) {
 throw new IllegalStateException("You can't delete element before first next() method call");
 }
 examples.remove(--index);
 }
}

• rolfl: In Java it is illegal to call remove() twice in a row, or without calling next() first. See this code I have written here for some ideas: github.com/hunterhacker/jdom/blob/master/core/src/java/org/…
• yegor256: this article may help you: yegor256.com/2015/04/30/iterating-adapter.html

Answer 1

I think your implementation is overall very good, two small comments:

• Improving readability for return statement in hasNext to return examples.size() != index;
• Making the examples field final: private final List<Vector> examples;

However, if the Vector class here is java.util.Vector you should know that it is considered deprecated in favor of the ArrayList class.

Also, since you create your iterator from a List<Vector> you could get an Iterator<Vector> by calling list.iterator();

• ashur: Well... I completely forgot about that I can call list.iterator(); :P. Thank you !