|
/*
* 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.ArrayList;
import java.util.Collections;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* @since 4.37
* @author Jaroslav Tulach
*/
public class Utils {
/**
* Concatenates the content of two enumerations into one.
* Until the
* end of <code>en1</code> is reached its elements are being served.
* As soon as the <code>en1</code> has no more elements, the content
* of <code>en2</code> is being returned.
*
* @param en1 first enumeration
* @param en2 second enumeration
* @return enumeration
*/
public static <T> Enumeration<T> concat(Enumeration<? extends T> en1, Enumeration<? extends T> en2) {
ArrayList<Enumeration<? extends T>> two = new ArrayList<Enumeration<? extends T>>();
two.add(en1);
two.add(en2);
return new SeqEn<T>(Collections.enumeration(two));
}
}
class SeqEn<T> extends Object implements Enumeration<T> {
/** enumeration of Enumerations */
private Enumeration<? extends Enumeration<? extends T>> en;
/** current enumeration */
private Enumeration<? extends T> current;
/** is {@link #current} up-to-date and has more elements?
* The combination <CODE>current == null</CODE> and
* <CODE>checked == true means there are no more elements
* in this enumeration.
*/
private boolean checked = false;
/** Constructs new enumeration from already existing. The elements
* of <CODE>en</CODE> should be also enumerations. The resulting
* enumeration contains elements of such enumerations.
*
* @param en enumeration of Enumerations that should be sequenced
*/
public SeqEn(Enumeration<? extends Enumeration <? extends T>> en) {
this.en = en;
}
/** Ensures that current enumeration is set. If there aren't more
* elements in the Enumerations, sets the field <CODE>current</CODE> to null.
*/
private void ensureCurrent() {
while ((current == null) || !current.hasMoreElements()) {
if (en.hasMoreElements()) {
current = en.nextElement();
} else {
// no next valid enumeration
current = null;
return;
}
}
}
/** @return true if we have more elements */
public boolean hasMoreElements() {
if (!checked) {
ensureCurrent();
checked = true;
}
return current != null;
}
/** @return next element
* @exception NoSuchElementException if there is no next element
*/
public T nextElement() {
if (!checked) {
ensureCurrent();
}
if (current != null) {
checked = false;
return current.nextElement();
} else {
checked = true;
throw new java.util.NoSuchElementException();
}
}
}
|
