Re: returning a pair of iterator.

"toton" <abirbasak@gmail.com> wrote in message
news:1159969205.595764.187530@b28g2000cwb.googlegroups.com...


    Have your elements implement some sort of interface which provides all
the "getter" and non mutating functionality, and have the iterator wrap the
elements in an immutable wrapper (or copy):

interface Foo {
  public int getX();
}

class MutableFoo implements Foo {
  private int myX;
  public int getX() {
    return myX;
  }
  public void setX(int newValue) {
    myX = newValue;
  }
}

class ImmutableFoo implements Foo {
  private final int myX;
  public ImmutableFoo(int value) {
    myX = value;
  }
  public ImmutableFoo(Foo value) {
    myX = value.getX();
  }
  public int getX() {
    return myX;
  }
}

class ConstIterator<Foo> implements Iterator<Foo> {
  private final Iterator<Foo> delegateIterator;

  public ConstIterator<Foo>(Iterator<Foo> delegate) {
    delegateIterator = delegate;
  }
  public boolean hasNext() {
    delegateIterator.hasNext();
  }
  public Foo next() {
    return new ImmutableFoo(delegateIterator.next());
  }
  public void remove() {
    /*I don't know what C++'s const_iterator does here, but you should be
able to figure it out from here on.*/
  }
}

    Note that a really determine programmer can still modify the elements
using sneaky stuff like reflection or JNI.

    - Oliver