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POCan ListIterator safely be susbtituted for Iterator? (Implementing a CopyOnWrite wrapper for List)
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copied!<p>I have many instance in code where a Collection, most usually a List is returned from a method and to account for the caller possibly altering that list, a defensive copy is made.</p> <p>The JDK does not seem to provide a wrapper for this purpose, so I'm trying to roll my own (Note: java.util.concurrent.CopyOnWriteArrayList is <em>not</em> what I'm looking for here).</p> <p>Schematically, what I'm trying is:</p> <pre><code>public class CopyOnWriteList<E> extends List<E> { protected List<E> list; protected boolean isCopied; public CopyOnWriteList(List<E> list) { this.list = list; } private void ensureCopy() { if (!isCopied) { list = new ArrayList<E>(list); isCopied = true; } } public E get(int i) { return list.get(i); } public boolean add(E e) { ensureCopy(); return list.add(e); } // ... many more simple methods } </code></pre> <p>For most of the API this is simple enough, but looking at java.util.ArrayList I found, that for the method iterator() it returns a different implementation than for listIterator(), although is ListIterator extends its Iterator and it <em>doesn't</em> add any new members.</p> <p>I wonder if there is a deeper reason behind this - I planned simply to implement iterator() and listIterator() all returning the same type of iterator - a ListIterator. Is there any logical reason why one should <em>not</em> return a ListIterator from the iterator()-method?</p>

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