core/src/org/apache/pivot/collections/EnumSet.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License,
 * Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.pivot.collections;

import java.io.Serializable;
import java.util.Comparator;
import java.util.Iterator;
import java.util.NoSuchElementException;

import org.apache.pivot.annotations.UnsupportedOperation;
import org.apache.pivot.util.ListenerList;

/**
 * Implementation of the {@link Set} interface that is backed by an array of
 * enum values.
 *
 * @param <E> The enum type contained in this set.
 */
public class EnumSet<E extends Enum<E>> implements Set<E>, Serializable {
    private static final long serialVersionUID = 3544488357505145448L;

    private class ElementIterator implements Iterator<E> {
        private int i = 0;
        private E next = null;

        @Override
        public boolean hasNext() {
            if (next == null) {
                while (i < elements.length && !members[i]) {
                    i++;
                }

                if (i < elements.length) {
                    next = elements[i];
                } else {
                    next = null;
                }
            }

            return (next != null);
        }

        @Override
        public E next() {
            if (!hasNext()) {
                throw new NoSuchElementException();
            }

            E nextLocal = this.next;
            this.next = null;
            i++;

            return nextLocal;
        }

        @Override
        @UnsupportedOperation
        public void remove() {
            throw new UnsupportedOperationException();
        }
    }

    private Class<E> enumClass;
    private E[] elements;
    private boolean[] members;
    private int count = 0;

    private transient SetListener.Listeners<E> setListeners = new SetListener.Listeners<>();

    public EnumSet(final Class<E> enumClass) {
        this.enumClass = enumClass;

        elements = enumClass.getEnumConstants();
        members = new boolean[elements.length];
    }

    public Class<E> getEnumClass() {
        return enumClass;
    }

    @Override
    public boolean add(final E element) {
        boolean added = false;

        int ordinal = element.ordinal();
        if (!members[ordinal]) {
            members[ordinal] = true;
            added = true;
            count++;

            setListeners.elementAdded(this, element);
        }

        return added;
    }

    @Override
    public boolean remove(final E element) {
        boolean removed = false;

        int ordinal = element.ordinal();
        if (members[ordinal]) {
            members[ordinal] = false;
            removed = true;
            count--;

            setListeners.elementRemoved(this, element);
        }

        return removed;
    }

    @Override
    public void clear() {
        if (count > 0) {
            members = new boolean[members.length];
            count = 0;
            setListeners.setCleared(this);
        }
    }

    @Override
    public boolean contains(final E element) {
        return members[element.ordinal()];
    }

    @Override
    public boolean isEmpty() {
        return count == 0;
    }

    @Override
    public int getCount() {
        return count;
    }

    @Override
    public Comparator<E> getComparator() {
        return null;
    }

    @Override
    @UnsupportedOperation
    public void setComparator(final Comparator<E> comparator) {
        throw new UnsupportedOperationException(
            "Cannot set a comparator because an Enum Set is always ordered by its underlying enum.");
    }

    @Override
    public Iterator<E> iterator() {
        return new ElementIterator();
    }

    @Override
    public ListenerList<SetListener<E>> getSetListeners() {
        return setListeners;
    }

    /**
     * Creates an empty enum set.
     *
     * @param <E> The enum type of the set.
     * @param elementClass The class of the individual elements to be used
     * in this set.
     * @return The new empty set.
     */
    public static <E extends Enum<E>> EnumSet<E> noneOf(final Class<E> elementClass) {
        return new EnumSet<E>(elementClass);
    }

    /**
     * Creates an enum set initially containing all the elements of the backing enum.
     *
     * @param <E> The enum type of the set.
     * @param elementClass The class of the individual elements to be used
     * in this set.
     * @return The new complete set.
     */
    public static <E extends Enum<E>> EnumSet<E> allOf(final Class<E> elementClass) {
        EnumSet<E> set = new EnumSet<E>(elementClass);
        for (E e : elementClass.getEnumConstants()) {
            set.add(e);
        }
        return set;
    }

    /**
     * Creates an enum set containing the given element.
     *
     * @param <E> The enum type of the set.
     * @param e The only element to assign to the new set.
     * @return The new set containing the single element.
     */
    public static <E extends Enum<E>> EnumSet<E> of(final E e) {
        EnumSet<E> set = new EnumSet<>(e.getDeclaringClass());
        set.add(e);
        return set;
    }

    /**
     * Creates an enum set containing the given elements.
     *
     * @param <E> The enum type of the set.
     * @param e1 The first element to add to the new set.
     * @param e2 The second element to add.
     * @return The new set containing only these two elements.
     */
    public static <E extends Enum<E>> EnumSet<E> of(final E e1, final E e2) {
        EnumSet<E> set = new EnumSet<>(e1.getDeclaringClass());
        set.add(e1);
        set.add(e2);
        return set;
    }

    /**
     * Creates an enum set containing the given elements.
     *
     * @param <E> The enum type of the set.
     * @param e1 The first element to add to the new set.
     * @param e2 The second element to add.
     * @param e3 The third element to add.
     * @return The new set containing only these three elements.
     */
    public static <E extends Enum<E>> EnumSet<E> of(final E e1, final E e2, final E e3) {
        EnumSet<E> set = new EnumSet<>(e1.getDeclaringClass());
        set.add(e1);
        set.add(e2);
        set.add(e3);
        return set;
    }

    /**
     * Creates an enum set containing the given elements.
     *
     * @param <E> The enum type of the set.
     * @param e1 The first element to add to the new set.
     * @param e2 The second element to add.
     * @param e3 The third element to add.
     * @param e4 The fourth element to add.
     * @return The new set containing only these four elements.
     */
    public static <E extends Enum<E>> EnumSet<E> of(final E e1, final E e2, final E e3, final E e4) {
        EnumSet<E> set = new EnumSet<>(e1.getDeclaringClass());
        set.add(e1);
        set.add(e2);
        set.add(e3);
        set.add(e4);
        return set;
    }

    /**
     * Adds all the elements of the given collection of this enum
     * to this set.
     *
     * @param c The other collection to add to this set.
     * @return Whether or not the enum set changed as a result.
     */
    public boolean addAll(final Collection<E> c) {
        boolean changed = false;
        for (E elem : c) {
            if (add(elem)) {
                changed = true;
            }
        }
        return changed;
    }
}