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Add specific classes (singleton) for empty cases 

Add toList and toArray
Rename certain methods to toXxx and asXxx


git-svn-id: https://svn.apache.org/repos/asf/jakarta/commons/proper/collections/trunk@130793 13f79535-47bb-0310-9956-ffa450edef68
This commit is contained in:
Stephen Colebourne 2002-08-17 22:14:22 +00:00
parent a24ad64d19
commit 5b1e839241
1 changed files with 193 additions and 22 deletions
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215
src/java/org/apache/commons/collections/IteratorUtils.java
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@ -1,7 +1,7 @@
/*
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/IteratorUtils.java,v 1.1 2002/08/17 11:38:53 scolebourne Exp $
* $Revision: 1.1 $
* $Date: 2002/08/17 11:38:53 $
* $Header: /home/jerenkrantz/tmp/commons/commons-convert/cvs/home/cvs/jakarta-commons//collections/src/java/org/apache/commons/collections/IteratorUtils.java,v 1.2 2002/08/17 22:14:22 scolebourne Exp $
* $Revision: 1.2 $
* $Date: 2002/08/17 22:14:22 $
*
* ====================================================================
*
@ -60,15 +60,19 @@
*/
package org.apache.commons.collections;
import java.lang.reflect.Array;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Dictionary;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import java.util.NoSuchElementException;
import org.apache.commons.collections.iterators.ArrayIterator;
import org.apache.commons.collections.iterators.CollatingIterator;
@ -87,13 +91,22 @@ import org.apache.commons.collections.iterators.TransformIterator;
* <code>org.apache.commons.collections.iterators</code> subpackage.
*
* @author <a href="mailto:scolebourne@joda.org">Stephen Colebourne</a>
* @version $Id: IteratorUtils.java,v 1.1 2002/08/17 11:38:53 scolebourne Exp $
* @version $Id: IteratorUtils.java,v 1.2 2002/08/17 22:14:22 scolebourne Exp $
* @since 2.1
*/
public class IteratorUtils {
// validation is done in this class in certain cases because the
// public classes allow invalid states
/**
* An iterator over no elements
*/
public static final Iterator EMPTY_ITERATOR = new EmptyIterator();
/**
* A list iterator over no elements
*/
public static final ListIterator EMPTY_LIST_ITERATOR = new EmptyListIterator();
/**
* Prevents instantiation.
*/
@ -109,7 +122,7 @@ public class IteratorUtils {
* @return an iterator over nothing
*/
public static Iterator emptyIterator() {
return Collections.EMPTY_LIST.iterator();
return EMPTY_ITERATOR;
}
/**
@ -121,7 +134,7 @@ public class IteratorUtils {
* @return a list iterator over nothing
*/
public static ListIterator emptyListIterator() {
return Collections.EMPTY_LIST.listIterator();
return EMPTY_LIST_ITERATOR;
}
/**
@ -383,25 +396,12 @@ public class IteratorUtils {
return new FilterListIterator(listIterator, predicate);
}
/**
* Gets a list iterator based on a simple iterator.
* <p>
* As the wrapped Iterator is traversed, a LinkedList of its values is
* cached, permitting all required operations of ListIterator.
*
* @param iterator the iterator to use, not null
* @throws NullPointerException if iterator parameter is null
*/
public static Iterator iteratorListIterator(Iterator iterator) {
return new ListIteratorWrapper(iterator);
}
/**
* Gets an iterator that provides an iterator view of the given enumeration.
*
* @param enumeration the enumeration to use
*/
public static Iterator enumerationIterator(Enumeration enumeration) {
public static Iterator asIterator(Enumeration enumeration) {
if (enumeration == null) {
throw new NullPointerException("Enumeration must not be null");
}
@ -415,7 +415,7 @@ public class IteratorUtils {
* @param enumeration the enumeration to use
* @param collection the collection to remove elements form
*/
public static Iterator enumerationIterator(Enumeration enumeration, Collection removeCollection) {
public static Iterator asIterator(Enumeration enumeration, Collection removeCollection) {
if (enumeration == null) {
throw new NullPointerException("Enumeration must not be null");
}
@ -431,13 +431,107 @@ public class IteratorUtils {
* @param iterator the iterator to use, not null
* @throws NullPointerException if iterator is null
*/
public static Enumeration iteratorEnumeration(Iterator iterator) {
public static Enumeration asEnumeration(Iterator iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
return new IteratorEnumeration(iterator);
}
/**
* Gets a list iterator based on a simple iterator.
* <p>
* As the wrapped Iterator is traversed, a LinkedList of its values is
* cached, permitting all required operations of ListIterator.
*
* @param iterator the iterator to use, not null
* @throws NullPointerException if iterator parameter is null
*/
public static ListIterator toListIterator(Iterator iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
return new ListIteratorWrapper(iterator);
}
/**
* Gets an array based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, this is converted to an array.
*
* @param iterator the iterator to use, not null
* @throws NullPointerException if iterator parameter is null
*/
public static Object[] toArray(Iterator iterator) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
List list = toList(iterator, 100);
return list.toArray();
}
/**
* Gets an array based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, this is converted to an array.
*
* @param iterator the iterator to use, not null
* @param arrayClass the class of array to create
* @throws NullPointerException if iterator parameter is null
* @throws NullPointerException if arrayClass is null
* @throws ClassCastException if the arrayClass is invalid
*/
public static Object[] toArray(Iterator iterator, Class arrayClass) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (arrayClass == null) {
throw new NullPointerException("Array class must not be null");
}
List list = toList(iterator, 100);
return list.toArray((Object[]) Array.newInstance(arrayClass, list.size()));
}
/**
* Gets a list based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, the list is returned.
*
* @param iterator the iterator to use, not null
* @throws NullPointerException if iterator parameter is null
*/
public static List toList(Iterator iterator) {
return toList(iterator, 10);
}
/**
* Gets a list based on an iterator.
* <p>
* As the wrapped Iterator is traversed, an ArrayList of its values is
* created. At the end, the list is returned.
*
* @param iterator the iterator to use, not null
* @param estimatedSize the initial size of the ArrayList
* @throws NullPointerException if iterator parameter is null
* @throws IllegalArgumentException if the size is less than 1
*/
public static List toList(Iterator iterator, int estimatedSize) {
if (iterator == null) {
throw new NullPointerException("Iterator must not be null");
}
if (estimatedSize < 1) {
throw new IllegalArgumentException("Estimated size must be greater than 0");
}
List list = new ArrayList(estimatedSize);
while (iterator.hasNext()) {
list.add(iterator.next());
}
return list;
}
/**
* Gets a suitable Iterator for the given object.
* <p>
@ -497,5 +591,82 @@ public class IteratorUtils {
return singletonIterator(obj);
}
}
/**
* EmptyIterator class
*/
static class EmptyIterator implements Iterator {
/**
* @see java.util.Iterator#hasNext()
*/
public boolean hasNext() {
return false;
}
/**
* @see java.util.Iterator#next()
*/
public Object next() {
throw new NoSuchElementException();
}
/**
* @see java.util.Iterator#remove()
*/
public void remove() {
throw new UnsupportedOperationException("remove() not supported for empty Iterator");
}
}
/**
* EmptyListIterator class
*/
static class EmptyListIterator extends EmptyIterator implements ListIterator {
/**
* @see java.util.ListIterator#hasPrevious()
*/
public boolean hasPrevious() {
return false;
}
/**
* @see java.util.ListIterator#previous()
*/
public Object previous() {
throw new NoSuchElementException();
}
/**
* @see java.util.ListIterator#nextIndex()
*/
public int nextIndex() {
return 0;
}
/**
* @see java.util.ListIterator#previousIndex()
*/
public int previousIndex() {
return -1;
}
/**
* @see java.util.ListIterator#add(Object)
*/
public void add(Object o) {
throw new UnsupportedOperationException("add() not supported for empty Iterator");
}
/**
* @see java.util.ListIterator#set(Object)
*/
public void set(Object o) {
throw new UnsupportedOperationException("set() not supported for empty Iterator");
}
}
}