Iterator Collection
// $Id: IteratorCollection.java,v 1.12 2004/11/29 19:10:44 grove Exp $
//package net.ontopia.utils;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
/**
* INTERNAL: A wrapper class for presenting a collection view on iterators. The
* wrapped iterator will be lazily traversed.</p>
*/
public class IteratorCollection<T> implements Collection<T> {
protected Iterator<T> iterator;
protected Collection<T> coll;
protected boolean resolved;
protected int iter_size = -1;
protected int max_size = Integer.MAX_VALUE;
public IteratorCollection(Iterator<T> iterator) {
this.iterator = iterator;
coll = new ArrayList<T>();
if (iterator.hasNext() && max_size > 0)
resolved = false;
else
resolved = true;
}
public IteratorCollection(Iterator<T> iterator, int size) {
this(iterator);
iter_size = size;
}
public IteratorCollection(Iterator<T> iterator, int size, int max_size) {
this(iterator, size);
if (max_size < 0)
this.max_size = 0;
else
this.max_size = max_size;
}
protected synchronized T nextObject() {
// Get next object in iterator
T object = iterator.next();
// Set resolved flag to true if this was the last object
int csize = coll.size();
if (!iterator.hasNext() || csize >= max_size
|| (iter_size > 0 && csize >= iter_size)) {
resolved = true;
iterator = null;
}
// Add object to collection
coll.add(object);
// Return the object
return object;
}
protected synchronized void resolve() {
while (iterator.hasNext()) {
int csize = coll.size();
if (csize >= max_size || (iter_size > 0 && csize >= iter_size))
break;
coll.add(iterator.next());
}
resolved = true;
iterator = null;
}
public void clear() {
coll.clear();
resolved = true;
iterator = null;
}
public boolean contains(Object o) {
if (coll.contains((T) o))
return true;
synchronized (this) {
while (!resolved) {
Object object = nextObject();
if (object == o)
return true;
}
}
return false;
}
public boolean containsAll(Collection<?> c) {
// FIXME: This one can be improved.
// If partially resolved collection contains all objects then we're fine
if (coll.containsAll(c))
return true;
// Otherwise resolve iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.containsAll(c);
}
public boolean isEmpty() {
// Collection is empty if; built collection or iterator contains
// elements
if (coll.size() > 0)
return false;
if (!resolved && iterator.hasNext() && max_size > 0)
return false;
return true;
}
public Iterator<T> iterator() {
// FIXME: This can be improved lot by lazily traversing internal
// iterator.
if (!resolved)
resolve();
return coll.iterator();
}
public int size() {
// If iterator has been resolved return the size of the collection
if (resolved)
return coll.size();
// If iterator has explicit size use that.
else if (iter_size >= 0) {
if (iter_size < max_size)
return iter_size;
else
return max_size;
}
// Last alternative is to traverse the entire iterator.
resolve();
return coll.size();
}
// --- Methods that require the entire iterator to be traversed.
public int hashCode() {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.hashCode();
}
public boolean equals(Object o) {
if (!(o instanceof Collection))
return false;
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.equals(o);
}
public Object[] toArray() {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.toArray();
}
public Object[] toArray(Object[] a) {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.toArray(a);
}
public boolean add(T o) {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.add(o);
}
public boolean addAll(Collection c) {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.addAll(c);
}
public boolean remove(Object o) {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.remove(o);
}
public boolean removeAll(Collection c) {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.removeAll(c);
}
public boolean retainAll(Collection c) {
// Traverse the entire iterator
if (!resolved)
resolve();
// Call method on nested collection
return coll.retainAll(c);
}
}
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