|
/*
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
*
* Copyright 1997-2007 Sun Microsystems, Inc. All rights reserved.
*
* The contents of this file are subject to the terms of either the GNU
* General Public License Version 2 only ("GPL") or the Common
* Development and Distribution License("CDDL") (collectively, the
* "License"). You may not use this file except in compliance with the
* License. You can obtain a copy of the License at
* http://www.netbeans.org/cddl-gplv2.html
* or nbbuild/licenses/CDDL-GPL-2-CP. See the License for the
* specific language governing permissions and limitations under the
* License. When distributing the software, include this License Header
* Notice in each file and include the License file at
* nbbuild/licenses/CDDL-GPL-2-CP. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the GPL Version 2 section of the License file that
* accompanied this code. If applicable, add the following below the
* License Header, with the fields enclosed by brackets [] replaced by
* your own identifying information:
* "Portions Copyrighted [year] [name of copyright owner]"
*
* Contributor(s):
*
* The Original Software is NetBeans. The Initial Developer of the Original
* Software is Sun Microsystems, Inc. Portions Copyright 1997-2006 Sun
* Microsystems, Inc. All Rights Reserved.
*
* If you wish your version of this file to be governed by only the CDDL
* or only the GPL Version 2, indicate your decision by adding
* "[Contributor] elects to include this software in this distribution
* under the [CDDL or GPL Version 2] license." If you do not indicate a
* single choice of license, a recipient has the option to distribute
* your version of this file under either the CDDL, the GPL Version 2 or
* to extend the choice of license to its licensees as provided above.
* However, if you add GPL Version 2 code and therefore, elected the GPL
* Version 2 license, then the option applies only if the new code is
* made subject to such option by the copyright holder.
*/
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;
/**
* @since 4.37
* @author Jaroslav Tulach
*/
final class Enumerations extends Object {
/**
* Filters the input enumeration to new one that should contain
* each of the provided elements just once.
* The elements are compared
* using their default <code>equals</code> and <code>hashCode</code> methods.
*
* @param en enumeration to filter
* @return enumeration without duplicated items
*/
public static <T> Enumeration<T> removeDuplicates(Enumeration<T> en) {
class RDupls implements Processor<T,T> {
private Set<T> set = new HashSet<T>();
public T process(T o, Collection<T> nothing) {
return set.add(o) ? o : null;
}
}
return filter(en, new RDupls());
}
/**
* Returns an enumeration that iterates over provided array.
* @param arr the array of object
* @return enumeration of those objects
*/
public static <T> Enumeration<T> array(T... arr) {
return Collections.enumeration(Arrays.asList(arr));
}
/**
* Removes all <code>null</code>s from the input enumeration.
* @param en enumeration that can contain nulls
* @return new enumeration without null values
*/
public static <T> Enumeration<T> removeNulls(Enumeration<T> en) {
return filter(en, new RNulls<T>());
}
/**
* For each element of the input enumeration <code>en</code> asks the
* {@link Processor} to provide a replacement.
* The <code>toAdd</code> argument of the processor is always null.
*
* Example to convert any objects into strings:
* <pre>
* Processor convertToString = new Processor() {
* public Object process(Object obj, Collection alwaysNull) {
* return obj.toString(); // converts to string
* }
* };
* Enumeration strings = Enumerations.convert(elems, convertToString);
* </pre>
*
* @param en enumeration of any objects
* @param processor a callback processor for the elements (its toAdd arguments is always null)
* @return new enumeration where all elements has been processed
*/
public static <T,R> Enumeration<R> convert(Enumeration<? extends T> en, Processor<T,R> processor) {
return new AltEn<T,R>(en, processor);
}
/**
* Filters some elements out from the input enumeration.
* Just make the
* {@link Processor} return <code>null</code>. Please notice the <code>toAdd</code>
* argument of the processor is always <code>null</code>.
*
* Example to remove all objects that are not strings:
* <pre>
* Processor onlyString = new Processor() {
* public Object process(Object obj, Collection alwaysNull) {
* if (obj instanceof String) {
* return obj;
* } else {
* return null;
* }
* }
* };
* Enumeration strings = Enumerations.filter(elems, onlyString);
* </pre>
*
* @param en enumeration of any objects
* @param filter a callback processor for the elements (its toAdd arguments is always null)
* @return new enumeration which does not include non-processed (returned null from processor) elements
* @see NbCollections#checkedEnumerationByFilter
*/
public static <T,R> Enumeration<R> filter(Enumeration<? extends T> en, Processor<T,R> filter) {
return new FilEn<T,R>(en, filter);
}
/**
* Support for breadth-first enumerating.
* Before any element is returned
* for the resulting enumeration it is processed in the {@link Processor} and
* the processor is allowed to modify it and also add additional elements
* at the (current) end of the <q>queue</q> by calling <code>toAdd.add</code>
* or <code>toAdd.addAll</code>. No other methods can be called on the
* provided <code>toAdd</code> collection.
*
* Example of doing breadth-first walk through a tree:
* <pre>
* Processor queueSubnodes = new Processor() {
* public Object process(Object obj, Collection toAdd) {
* Node n = (Node)obj;
* toAdd.addAll (n.getChildrenList());
* return n;
* }
* };
* Enumeration strings = Enumerations.queue(elems, queueSubnodes);
* </pre>
*
* @param en initial content of the resulting enumeration
* @param filter the processor that is called for each element and can
* add and addAll elements to its toAdd Collection argument and
* also change the value to be returned
* @return enumeration with the initial and queued content (it can contain
* <code>null</code> if the filter returned <code>null</code> from its
* {@link Processor#process} method.
*/
public static <T,R> Enumeration<R> queue(Enumeration<? extends T> en, Processor<T,R> filter) {
QEn<T,R> q = new QEn<T,R>(filter);
while (en.hasMoreElements()) {
q.put(en.nextElement());
}
return q;
}
/**
* Processor interface that can filter out objects from the enumeration,
* change them or add aditional objects to the end of the current enumeration.
*/
public static interface Processor<T,R> {
/** @param original the object that is going to be returned from the enumeration right now
* @return a replacement for this object
* @param toAdd can be non-null if one can add new objects at the end of the enumeration
*/
public R process(T original, Collection<T> toAdd);
}
/** Altering enumeration implementation */
private static final class AltEn<T,R> extends Object implements Enumeration<R> {
/** enumeration to filter */
private Enumeration<? extends T> en;
/** map to alter */
private Processor<T,R> process;
/**
* @param en enumeration to filter
*/
public AltEn(Enumeration<? extends T> en, Processor<T,R> process) {
this.en = en;
this.process = process;
}
/** @return true if there is more elements in the enumeration
*/
public boolean hasMoreElements() {
return en.hasMoreElements();
}
/** @return next object in the enumeration
* @exception NoSuchElementException can be thrown if there is no next object
* in the enumeration
*/
public R nextElement() {
return process.process(en.nextElement(), null);
}
}
// end of AltEn
/** QueueEnumeration
*/
private static class QEn<T,R> extends Object implements Enumeration<R> {
/** next object to be returned */
private ListItem<T> next = null;
/** last object in the queue */
private ListItem<T> last = null;
/** processor to use */
private Processor<T,R> processor;
public QEn(Processor<T,R> p) {
this.processor = p;
}
/** Put adds new object to the end of queue.
* @param o the object to add
*/
public void put(T o) {
if (last != null) {
ListItem<T> li = new ListItem<T>(o);
last.next = li;
last = li;
} else {
next = last = new ListItem<T>(o);
}
}
/** Adds array of objects into the queue.
* @param arr array of objects to put into the queue
*/
public void put(Collection<? extends T> arr) {
for (T e : arr) {
put(e);
}
}
/** Is there any next object?
* @return true if there is next object, false otherwise
*/
public boolean hasMoreElements() {
return next != null;
}
/** @return next object in enumeration
* @exception NoSuchElementException if there is no next object
*/
public R nextElement() {
if (next == null) {
throw new NoSuchElementException();
}
T res = next.object;
if ((next = next.next) == null) {
last = null;
}
;
ToAdd<T,R> toAdd = new ToAdd<T,R>(this);
R out = processor.process(res, toAdd);
toAdd.finish();
return out;
}
/** item in linked list of Objects */
private static final class ListItem<T> {
T object;
ListItem<T> next;
/** @param o the object for this item */
ListItem(T o) {
object = o;
}
}
/** Temporary collection that supports only add and addAll operations*/
private static final class ToAdd<T,R> extends Object implements Collection<T> {
private QEn<T,R> q;
public ToAdd(QEn<T,R> q) {
this.q = q;
}
public void finish() {
this.q = null;
}
public boolean add(T o) {
q.put(o);
return true;
}
public boolean addAll(Collection<? extends T> c) {
q.put(c);
return true;
}
private String msg() {
return "Only add and addAll are implemented"; // NOI18N
}
public void clear() {
throw new UnsupportedOperationException(msg());
}
public boolean contains(Object o) {
throw new UnsupportedOperationException(msg());
}
public boolean containsAll(Collection c) {
throw new UnsupportedOperationException(msg());
}
public boolean isEmpty() {
throw new UnsupportedOperationException(msg());
}
public Iterator<T> iterator() {
throw new UnsupportedOperationException(msg());
}
public boolean remove(Object o) {
throw new UnsupportedOperationException(msg());
}
public boolean removeAll(Collection c) {
throw new UnsupportedOperationException(msg());
}
public boolean retainAll(Collection c) {
throw new UnsupportedOperationException(msg());
}
public int size() {
throw new UnsupportedOperationException(msg());
}
public Object[] toArray() {
throw new UnsupportedOperationException(msg());
}
public<X> X[] toArray(X[] a) {
throw new UnsupportedOperationException(msg());
}
}
// end of ToAdd
}
// end of QEn
/** Filtering enumeration */
private static final class FilEn<T,R> extends Object implements Enumeration<R> {
/** marker object stating there is no nexte element prepared */
private static final Object EMPTY = new Object();
/** enumeration to filter */
private Enumeration<? extends T> en;
/** element to be returned next time or {@link #EMPTY} if there is
* no such element prepared */
private R next = empty();
/** the set to use as filter */
private Processor<T,R> filter;
/**
* @param en enumeration to filter
*/
public FilEn(Enumeration<? extends T> en, Processor<T,R> filter) {
this.en = en;
this.filter = filter;
}
/** @return true if there is more elements in the enumeration
*/
public boolean hasMoreElements() {
if (next != empty()) {
// there is a object already prepared
return true;
}
while (en.hasMoreElements()) {
// read next
next = filter.process(en.nextElement(), null);
if (next != null) {
// if the object is accepted
return true;
}
;
}
next = empty();
return false;
}
/** @return next object in the enumeration
* @exception NoSuchElementException can be thrown if there is no next object
* in the enumeration
*/
public R nextElement() {
if ((next == EMPTY) && !hasMoreElements()) {
throw new NoSuchElementException();
}
R res = next;
next = empty();
return res;
}
@SuppressWarnings("unchecked")
private R empty() {
return (R)EMPTY;
}
}
// end of FilEn
/** Returns true from contains if object is not null */
private static class RNulls<T> implements Processor<T,T> {
public T process(T original, Collection<T> toAdd) {
return original;
}
}
// end of RNulls
}
|