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package com.day.util;
import java.util.Iterator;
/**
* Implements the Iterator interface and combines two
* Iterator objects into one single Iterator.
*
* The constructor takes two Iterator arguments: parent
* and child. Calling {@link #next} on this Iterator
* will first try to return an element from the parent Iterator
* and once the parent Iterator does not have any more elements
* it will return elements from the child Iterator.
*
* @version $Revision: 1.2 $, $Date: 2004-08-22 06:56:09 +0200 (Sun, 22 Aug 2004) $
* @author mreutegg
* @since fennec
* Audience wad
*/
public class CompoundIterator implements Iterator {
/**
* The parent Iterator. Elements from this
* Iterator are returned first.
*/
private final Iterator parent;
/**
* The child Iterator. Elements from this
* Iterator are returned, after the parent
* Iterator does not have elements any more.
*/
private final Iterator child;
/**
* Creates a CompoundIterator based on parent
* and child. This CompountIterator will first
* return elements from parent and then elements from
* child.
* @param parent the Iterator from where to return the elements
* first.
* @param child the Iterator from where to return the elements
* after parent does not have elements any more.
*/
public CompoundIterator(Iterator parent, Iterator child) {
this.parent = parent;
this.child = child;
}
/**
* Returns true if either parent or child iterator
* has a next element; false otherwise.
* @return true if either parent or child iterator
* has a next element; false otherwise.
*/
public boolean hasNext() {
return parent.hasNext() || child.hasNext();
}
/**
* Returns the next element from the parent or the child
* iterator object.
* @return the next element from the parent or the child
* iterator object.
*/
public Object next() {
return (parent.hasNext()) ? parent.next() : child.next();
}
/**
* Always throws UnsupportedOperationException
* @throws UnsupportedOperationException always!
*/
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException("remove() is not supported in CompoundInterator");
}
}