com.sun.xml.xsom.util.DeferedCollection Maven / Gradle / Ivy
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package com.sun.xml.xsom.util;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
/**
* {@link Collection} that returns the view of objects which are actually fetched
* lazily from an {@link Iterator}.
*
* @author Kohsuke Kawaguchi
*/
public class DeferedCollection implements Collection {
/**
* The iterator that lazily evaluates SCD query.
*/
private final Iterator result;
/**
* Stores values that are already fetched from {@link #result}.
*/
private final List archive = new ArrayList();
public DeferedCollection(Iterator result) {
this.result = result;
}
public boolean isEmpty() {
if(archive.isEmpty())
fetch();
return archive.isEmpty();
}
public int size() {
fetchAll();
return archive.size();
}
public boolean contains(Object o) {
if(archive.contains(o))
return true;
while(result.hasNext()) {
T value = result.next();
archive.add(value);
if(value.equals(o))
return true;
}
return false;
}
public boolean containsAll(Collection c) {
for (Object o : c) {
if(!contains(o))
return false;
}
return true;
}
public Iterator iterator() {
return new Iterator() {
int idx=0;
public boolean hasNext() {
if(idxT[] toArray(T[] a) {
fetchAll();
return archive.toArray(a);
}
private void fetchAll() {
while(result.hasNext())
archive.add(result.next());
}
/**
* Fetches another item from {@link
*/
private void fetch() {
if(result.hasNext())
archive.add(result.next());
}
// mutation methods are unsupported
public boolean add(T o) {
throw new UnsupportedOperationException();
}
public boolean remove(Object o) {
throw new UnsupportedOperationException();
}
public boolean addAll(Collection c) {
throw new UnsupportedOperationException();
}
public boolean removeAll(Collection c) {
throw new UnsupportedOperationException();
}
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException();
}
public void clear() {
throw new UnsupportedOperationException();
}
}