# HG changeset patch
# User Jesse Glick <jglick@netbeans.org>
# Date 1264632383 18000
# Node ID b3ae88304dd059b987d103e8d3552c0af70b815f
# Parent  03dc6e747bb8e21715539de2715ac58d24f4eb45
Checking params for null.

diff -r 03dc6e747bb8 -r b3ae88304dd0 openide.util/src/org/openide/util/Enumerations.java
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/openide.util/src/org/openide/util/Enumerations.java	Wed Jan 27 17:46:23 2010 -0500
@@ -0,0 +1,601 @@
+/*
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
+ *
+ * Copyright 1997-2009 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.
+ */
+
+package org.openide.util;
+
+import java.util.ArrayList;
+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;
+
+/**
+ * Factory methods for various types of {@link Enumeration}.
+ * Allows composition of existing enumerations, filtering their contents, and/or modifying them.
+ * All of this is designed to be done lazily, i.e. elements created on demand.
+ * @since 4.37
+ * @author Jaroslav Tulach
+ * @see NbCollections#checkedEnumerationByFilter
+ * @see NbCollections#iterable(Enumeration)
+ */
+public final class Enumerations extends Object {
+    /** No instances */
+    private Enumerations() {
+    }
+
+    /**
+     * An empty enumeration.
+     * Always returns <code>false</code> from
+     * <code>empty().hasMoreElements()</code> and throws <code>NoSuchElementException</code>
+     * from <code>empty().nextElement()</code>.
+     * @return the enumeration
+     */
+    public static final <T> Enumeration<T> empty() {
+        Collection<T> emptyL = Collections.emptyList();
+        return Collections.enumeration(emptyL);
+    }
+
+    /**
+     * Creates an enumeration with one element.
+     * @param obj the element to be present in the enumeration.
+     * @return enumeration
+     */
+    public static <T> Enumeration<T> singleton(T obj) {
+        return Collections.enumeration(Collections.singleton(obj));
+    }
+
+    /**
+     * 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));
+    }
+
+    /**
+     * Concatenates the content of many enumerations.
+     * The input value
+     * is enumeration of Enumeration elements and the result is composed
+     * all their content. Each of the provided enumeration is fully read
+     * and their content returned before the next enumeration is asked for
+     * their elements.
+     *
+     * @param enumOfEnums Enumeration of Enumeration elements
+     * @return enumeration
+     */
+    public static <T> Enumeration<T> concat(Enumeration<? extends Enumeration<? extends T>> enumOfEnums) {
+        return new SeqEn<T>(enumOfEnums);
+    }
+
+    /**
+     * 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.
+     * <p>
+     * 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>.
+     * <p>
+     * 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) {
+        Parameters.notNull("en", en);
+        Parameters.notNull("filter", 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.
+     * <p>
+     * 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
+
+    /** Sequence of enumerations */
+    private static final 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();
+            }
+        }
+    }
+     // end of SeqEn
+
+    /** 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
+}