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HHH-6423 : Add JoinedIterable<T>

This commit is contained in:
Gail Badner 2011-08-03 17:06:54 -07:00
parent 660a7cbef1
commit 2d52494b90
2 changed files with 251 additions and 0 deletions
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112
hibernate-core/src/main/java/org/hibernate/internal/util/collections/JoinedIterable.java Normal file
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/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2011, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.internal.util.collections;
import java.util.Iterator;
import java.util.List;
/**
* An JoinedIterable is an Iterable that wraps a number of Iterables.
*
* This class makes multiple iterables look like one to the caller.
* When any method from the Iterator interface is called on the
* Iterator object returned by {@link #iterator()}, the JoinedIterable
* will delegate to a single underlying Iterator. The JoinedIterable will
* invoke the iterator on each Iterable, in sequence, until all Iterators
* are exhausted.
*
* @author Gail Badner (adapted from JoinedIterator)
*/
public class JoinedIterable<T> implements Iterable<T> {
private final TypeSafeJoinedIterator<T> iterator;
public JoinedIterable(List<Iterable<T>> iterables) {
if ( iterables == null ) {
throw new NullPointerException( "Unexpected null iterables argument" );
}
iterator = new TypeSafeJoinedIterator<T>( iterables );
}
public Iterator<T> iterator() {
return iterator;
}
private class TypeSafeJoinedIterator<T> implements Iterator<T> {
// wrapped iterators
private List<Iterable<T>> iterables;
// index of current iterator in the wrapped iterators array
private int currentIterableIndex;
// the current iterator
private Iterator<T> currentIterator;
// the last used iterator
private Iterator<T> lastUsedIterator;
public TypeSafeJoinedIterator(List<Iterable<T>> iterables) {
this.iterables = iterables;
}
public boolean hasNext() {
updateCurrentIterator();
return currentIterator.hasNext();
}
public T next() {
updateCurrentIterator();
return currentIterator.next();
}
public void remove() {
updateCurrentIterator();
lastUsedIterator.remove();
}
// call this before any Iterator method to make sure that the current Iterator
// is not exhausted
@SuppressWarnings( {"unchecked"})
protected void updateCurrentIterator() {
if ( currentIterator == null) {
if( iterables.size() == 0 ) {
currentIterator = EmptyIterator.INSTANCE;
}
else {
currentIterator = iterables.get( 0 ).iterator();
}
// set last used iterator here, in case the user calls remove
// before calling hasNext() or next() (although they shouldn't)
lastUsedIterator = currentIterator;
}
while (! currentIterator.hasNext() && currentIterableIndex < iterables.size() - 1) {
currentIterableIndex++;
currentIterator = iterables.get( currentIterableIndex ).iterator();
}
}
}
}

139
hibernate-core/src/test/java/org/hibernate/test/util/JoinedIterableTest.java Normal file
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/*
* Hibernate, Relational Persistence for Idiomatic Java
*
* Copyright (c) 2011, Red Hat Inc. or third-party contributors as
* indicated by the @author tags or express copyright attribution
* statements applied by the authors. All third-party contributions are
* distributed under license by Red Hat Inc.
*
* This copyrighted material is made available to anyone wishing to use, modify,
* copy, or redistribute it subject to the terms and conditions of the GNU
* Lesser General Public License, as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
* or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
* for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this distribution; if not, write to:
* Free Software Foundation, Inc.
* 51 Franklin Street, Fifth Floor
* Boston, MA 02110-1301 USA
*/
package org.hibernate.test.util;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;
import org.junit.Test;
import org.hibernate.internal.util.collections.JoinedIterable;
import org.hibernate.testing.junit4.BaseUnitTestCase;
import static org.junit.Assert.assertEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertSame;
import static org.junit.Assert.assertTrue;
import static org.junit.Assert.fail;
/**
* @author Steve Ebersole
*/
public class JoinedIterableTest extends BaseUnitTestCase {
@Test
public void testNullIterables() {
try {
new JoinedIterable<String>( null );
fail();
}
catch (NullPointerException ex) {
// expected
}
}
@Test
public void testSingleEmptyIterable() {
Set<String> emptyList = new HashSet<String>();
List<Iterable<String>> iterableSets = new ArrayList<Iterable<String>>( );
iterableSets.add( emptyList );
Iterable<String> iterable = new JoinedIterable<String>( iterableSets );
assertFalse( iterable.iterator().hasNext() );
try {
iterable.iterator().next();
fail( "Should have thrown NoSuchElementException because the underlying collection is empty.");
}
catch ( NoSuchElementException ex ) {
// expected
}
try {
iterable.iterator().remove();
fail( "Should have thrown IllegalStateException because the underlying collection is empty." );
}
catch ( IllegalStateException ex ) {
// expected
}
for ( String s : iterable ) {
fail( "Should not have entered loop because underlying collection is empty");
}
}
@Test
public void testSingleIterableOfSingletonCollection() {
final String str = "a string";
Set<String> singleTonSet = new HashSet<String>( 1 );
singleTonSet.add( str );
List<Iterable<String>> iterableSets = new ArrayList<Iterable<String>>( );
iterableSets.add( singleTonSet );
Iterable<String> iterable = new JoinedIterable<String>( iterableSets );
assertTrue( iterable.iterator().hasNext() );
assertSame( str, iterable.iterator().next() );
assertFalse( iterable.iterator().hasNext() );
try {
iterable.iterator().next();
fail( "Should have thrown NoSuchElementException because the underlying collection is empty.");
}
catch ( NoSuchElementException ex ) {
// expected
}
for ( String s : iterable ) {
fail( "should not have entered loop because underlying iterator should have been exhausted." );
}
assertEquals( 1, singleTonSet.size() );
iterable = new JoinedIterable<String>( iterableSets );
for ( String s : iterable ) {
assertSame( str, s );
iterable.iterator().remove();
}
assertTrue( singleTonSet.isEmpty() );
}
@Test
public void testJoinedIterables() {
List<Iterable<Integer>> listOfIterables = new ArrayList<Iterable<Integer>>( );
List<Integer> twoElementList = Arrays.asList( 0, 1 );
listOfIterables.add( twoElementList );
List<Integer> emptyList = new ArrayList<Integer>( );
listOfIterables.add( emptyList );
List<Integer> oneElementList = Arrays.asList( 2 );
listOfIterables.add( oneElementList );
List<Integer> threeElementList = Arrays.asList( 3, 4, 5 );
listOfIterables.add( threeElementList );
JoinedIterable<Integer> joinedIterable = new JoinedIterable<Integer>( listOfIterables );
int i = 0;
for ( Integer val : joinedIterable ) {
assertEquals( Integer.valueOf( i ), val );
i++;
}
}
}