HHH-6423 : Add JoinedIterable<T>
This commit is contained in:
Gail Badner
parent
660a7cbef1
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2d52494b90
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/*
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* Hibernate, Relational Persistence for Idiomatic Java
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*
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* Copyright (c) 2011, Red Hat Inc. or third-party contributors as
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* indicated by the @author tags or express copyright attribution
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* statements applied by the authors. All third-party contributions are
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* distributed under license by Red Hat Inc.
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*
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* This copyrighted material is made available to anyone wishing to use, modify,
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* copy, or redistribute it subject to the terms and conditions of the GNU
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* Lesser General Public License, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
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* for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this distribution; if not, write to:
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* Free Software Foundation, Inc.
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02110-1301 USA
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*/
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package org.hibernate.internal.util.collections;
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import java.util.Iterator;
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import java.util.List;
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/**
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* An JoinedIterable is an Iterable that wraps a number of Iterables.
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*
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* This class makes multiple iterables look like one to the caller.
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* When any method from the Iterator interface is called on the
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* Iterator object returned by {@link #iterator()}, the JoinedIterable
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* will delegate to a single underlying Iterator. The JoinedIterable will
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* invoke the iterator on each Iterable, in sequence, until all Iterators
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* are exhausted.
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*
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* @author Gail Badner (adapted from JoinedIterator)
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*/
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public class JoinedIterable<T> implements Iterable<T> {
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private final TypeSafeJoinedIterator<T> iterator;
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public JoinedIterable(List<Iterable<T>> iterables) {
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if ( iterables == null ) {
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throw new NullPointerException( "Unexpected null iterables argument" );
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}
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iterator = new TypeSafeJoinedIterator<T>( iterables );
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}
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public Iterator<T> iterator() {
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return iterator;
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}
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private class TypeSafeJoinedIterator<T> implements Iterator<T> {
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// wrapped iterators
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private List<Iterable<T>> iterables;
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// index of current iterator in the wrapped iterators array
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private int currentIterableIndex;
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// the current iterator
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private Iterator<T> currentIterator;
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// the last used iterator
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private Iterator<T> lastUsedIterator;
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public TypeSafeJoinedIterator(List<Iterable<T>> iterables) {
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this.iterables = iterables;
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}
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public boolean hasNext() {
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updateCurrentIterator();
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return currentIterator.hasNext();
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}
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public T next() {
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updateCurrentIterator();
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return currentIterator.next();
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}
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public void remove() {
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updateCurrentIterator();
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lastUsedIterator.remove();
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}
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// call this before any Iterator method to make sure that the current Iterator
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// is not exhausted
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@SuppressWarnings( {"unchecked"})
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protected void updateCurrentIterator() {
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if ( currentIterator == null) {
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if( iterables.size() == 0 ) {
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currentIterator = EmptyIterator.INSTANCE;
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}
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else {
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currentIterator = iterables.get( 0 ).iterator();
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}
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// set last used iterator here, in case the user calls remove
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// before calling hasNext() or next() (although they shouldn't)
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lastUsedIterator = currentIterator;
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}
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while (! currentIterator.hasNext() && currentIterableIndex < iterables.size() - 1) {
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currentIterableIndex++;
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currentIterator = iterables.get( currentIterableIndex ).iterator();
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}
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}
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}
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}
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@ -0,0 +1,139 @@
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/*
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* Hibernate, Relational Persistence for Idiomatic Java
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*
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* Copyright (c) 2011, Red Hat Inc. or third-party contributors as
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* indicated by the @author tags or express copyright attribution
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* statements applied by the authors. All third-party contributions are
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* distributed under license by Red Hat Inc.
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*
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* This copyrighted material is made available to anyone wishing to use, modify,
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* copy, or redistribute it subject to the terms and conditions of the GNU
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* Lesser General Public License, as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
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* for more details.
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*
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* You should have received a copy of the GNU Lesser General Public License
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* along with this distribution; if not, write to:
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* Free Software Foundation, Inc.
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* 51 Franklin Street, Fifth Floor
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* Boston, MA 02110-1301 USA
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*/
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package org.hibernate.test.util;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.HashSet;
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import java.util.List;
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import java.util.NoSuchElementException;
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import java.util.Set;
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import org.junit.Test;
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import org.hibernate.internal.util.collections.JoinedIterable;
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import org.hibernate.testing.junit4.BaseUnitTestCase;
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import static org.junit.Assert.assertEquals;
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import static org.junit.Assert.assertFalse;
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import static org.junit.Assert.assertSame;
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import static org.junit.Assert.assertTrue;
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import static org.junit.Assert.fail;
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/**
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* @author Steve Ebersole
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*/
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public class JoinedIterableTest extends BaseUnitTestCase {
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@Test
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public void testNullIterables() {
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try {
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new JoinedIterable<String>( null );
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fail();
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}
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catch (NullPointerException ex) {
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// expected
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}
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}
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@Test
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public void testSingleEmptyIterable() {
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Set<String> emptyList = new HashSet<String>();
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List<Iterable<String>> iterableSets = new ArrayList<Iterable<String>>( );
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iterableSets.add( emptyList );
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Iterable<String> iterable = new JoinedIterable<String>( iterableSets );
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assertFalse( iterable.iterator().hasNext() );
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try {
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iterable.iterator().next();
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fail( "Should have thrown NoSuchElementException because the underlying collection is empty.");
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}
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catch ( NoSuchElementException ex ) {
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// expected
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}
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try {
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iterable.iterator().remove();
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fail( "Should have thrown IllegalStateException because the underlying collection is empty." );
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}
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catch ( IllegalStateException ex ) {
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// expected
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}
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for ( String s : iterable ) {
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fail( "Should not have entered loop because underlying collection is empty");
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}
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}
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@Test
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public void testSingleIterableOfSingletonCollection() {
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final String str = "a string";
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Set<String> singleTonSet = new HashSet<String>( 1 );
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singleTonSet.add( str );
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List<Iterable<String>> iterableSets = new ArrayList<Iterable<String>>( );
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iterableSets.add( singleTonSet );
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Iterable<String> iterable = new JoinedIterable<String>( iterableSets );
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assertTrue( iterable.iterator().hasNext() );
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assertSame( str, iterable.iterator().next() );
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assertFalse( iterable.iterator().hasNext() );
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try {
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iterable.iterator().next();
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fail( "Should have thrown NoSuchElementException because the underlying collection is empty.");
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}
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catch ( NoSuchElementException ex ) {
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// expected
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}
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for ( String s : iterable ) {
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fail( "should not have entered loop because underlying iterator should have been exhausted." );
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}
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assertEquals( 1, singleTonSet.size() );
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iterable = new JoinedIterable<String>( iterableSets );
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for ( String s : iterable ) {
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assertSame( str, s );
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iterable.iterator().remove();
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}
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assertTrue( singleTonSet.isEmpty() );
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}
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@Test
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public void testJoinedIterables() {
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List<Iterable<Integer>> listOfIterables = new ArrayList<Iterable<Integer>>( );
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List<Integer> twoElementList = Arrays.asList( 0, 1 );
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listOfIterables.add( twoElementList );
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List<Integer> emptyList = new ArrayList<Integer>( );
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listOfIterables.add( emptyList );
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List<Integer> oneElementList = Arrays.asList( 2 );
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listOfIterables.add( oneElementList );
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List<Integer> threeElementList = Arrays.asList( 3, 4, 5 );
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listOfIterables.add( threeElementList );
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JoinedIterable<Integer> joinedIterable = new JoinedIterable<Integer>( listOfIterables );
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int i = 0;
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for ( Integer val : joinedIterable ) {
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assertEquals( Integer.valueOf( i ), val );
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i++;
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}
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}
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}
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