/*
* ConcatenatedIterator.java
*/
package polyglot.util;
import java.util.Iterator;
/**
* ConcatenatedIterator
*
* Overview:
* This iterator wraps other iterators, and returns all their elements
* in order.
*
* Does not support Remove.
**/
public final class ConcatenatedIterator implements Iterator {
/**
* Constructs a new ConcatenatedIterator which yields all of the
* elements of <iter1>, followed by all the elements of <iter2>.
**/
public ConcatenatedIterator(Iterator iter1, Iterator iter2) {
this(new Iterator[]{iter1, iter2});
}
/**
* Constructs a new ConcatenatedIterator which yields every element, in
* order, of every element of the array iters, in order.
**/
public ConcatenatedIterator(Iterator[] iters) {
this.backing_iterators = (Iterator[]) iters.clone();
findNextItem();
}
/**
* Constructs a new ConcatenatedIterator which yields every element, in
* order, of every element of the collection iters, in order.
**/
public ConcatenatedIterator(java.util.Collection iters) {
this.backing_iterators = (Iterator[])iters.toArray(new Iterator[0]);
findNextItem();
}
public Object next() {
Object res = next_item;
if (res == null)
throw new java.util.NoSuchElementException();
findNextItem();
return res;
}
public boolean hasNext() {
return next_item != null;
}
public void remove() {
throw new UnsupportedOperationException("ConcatenatedIterator.remove");
}
// Advances the internal iterator.
private void findNextItem() {
while(index < backing_iterators.length) {
Iterator it = backing_iterators[index];
if (it.hasNext()) {
next_item = it.next();
return;
} else {
index++;
}
}
next_item = null;
}
// AF: if next_item==null, this iterator has no more elts to yield.
// otherwise, this iterator will yield next_item, followed by the
// remaining elements of backing_iterators[index], followed by the
// elements of backing_iterators[index+1]...
Object next_item;
Iterator[] backing_iterators;
int index;
}