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DistinctIterator.java
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DistinctIterator.java
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/*
* Copyright (c) 2022 Goldman Sachs and others.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* and Eclipse Distribution License v. 1.0 which accompany this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*/
package org.eclipse.collections.impl.lazy.iterator;
import java.util.Iterator;
import java.util.NoSuchElementException;
import org.eclipse.collections.api.factory.Sets;
import org.eclipse.collections.api.set.MutableSet;
public final class DistinctIterator<T>
implements Iterator<T>
{
private static final Object NULL = new Object();
private final Iterator<T> iterator;
private final MutableSet<T> seenSoFar = Sets.mutable.empty();
private Object next = NULL;
public DistinctIterator(Iterable<T> iterable)
{
this(iterable.iterator());
}
public DistinctIterator(Iterator<T> iterator)
{
this.iterator = iterator;
}
@Override
public void remove()
{
throw new UnsupportedOperationException("Cannot remove from a distinct iterator");
}
@Override
public boolean hasNext()
{
if (this.next != NULL)
{
return true;
}
while (this.iterator.hasNext())
{
T temp = this.iterator.next();
if (this.seenSoFar.add(temp))
{
this.next = temp;
return true;
}
}
return false;
}
@Override
public T next()
{
if (this.next != NULL || this.hasNext())
{
Object temp = this.next;
this.next = NULL;
return (T) temp;
}
throw new NoSuchElementException();
}
}