001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.lang3;
018    
019    import java.util.ArrayList;
020    import java.util.Arrays;
021    import java.util.LinkedHashMap;
022    import java.util.List;
023    import java.util.Map;
024    import java.util.EnumSet;
025    
026    /**
027     * <p>Utility library to provide helper methods for Java enums.</p>
028     *
029     * <p>#ThreadSafe#</p>
030     *
031     * @since 3.0
032     * @version $Id: EnumUtils.java 1199894 2011-11-09 17:53:59Z ggregory $
033     */
034    public class EnumUtils {
035    
036        /**
037         * This constructor is public to permit tools that require a JavaBean
038         * instance to operate.
039         */
040        public EnumUtils() {
041        }
042    
043        /**
044         * <p>Gets the {@code Map} of enums by name.</p>
045         *
046         * <p>This method is useful when you need a map of enums by name.</p>
047         *
048         * @param <E> the type of the enumeration
049         * @param enumClass  the class of the enum to query, not null
050         * @return the modifiable map of enum names to enums, never null
051         */
052        public static <E extends Enum<E>> Map<String, E> getEnumMap(Class<E> enumClass) {
053            Map<String, E> map = new LinkedHashMap<String, E>();
054            for (E e: enumClass.getEnumConstants()) {
055                map.put(e.name(), e);
056            }
057            return map;
058        }
059    
060        /**
061         * <p>Gets the {@code List} of enums.</p>
062         *
063         * <p>This method is useful when you need a list of enums rather than an array.</p>
064         *
065         * @param <E> the type of the enumeration
066         * @param enumClass  the class of the enum to query, not null
067         * @return the modifiable list of enums, never null
068         */
069        public static <E extends Enum<E>> List<E> getEnumList(Class<E> enumClass) {
070            return new ArrayList<E>(Arrays.asList(enumClass.getEnumConstants()));
071        }
072    
073        /**
074         * <p>Checks if the specified name is a valid enum for the class.</p>
075         *
076         * <p>This method differs from {@link Enum#valueOf} in that checks if the name is
077         * a valid enum without needing to catch the exception.</p>
078         *
079         * @param <E> the type of the enumeration
080         * @param enumClass  the class of the enum to query, not null
081         * @param enumName   the enum name, null returns false
082         * @return true if the enum name is valid, otherwise false
083         */
084        public static <E extends Enum<E>> boolean isValidEnum(Class<E> enumClass, String enumName) {
085            if (enumName == null) {
086                return false;
087            }
088            try {
089                Enum.valueOf(enumClass, enumName);
090                return true;
091            } catch (IllegalArgumentException ex) {
092                return false;
093            }
094        }
095    
096        /**
097         * <p>Gets the enum for the class, returning {@code null} if not found.</p>
098         *
099         * <p>This method differs from {@link Enum#valueOf} in that it does not throw an exception
100         * for an invalid enum name.</p>
101         *
102         * @param <E> the type of the enumeration
103         * @param enumClass  the class of the enum to query, not null
104         * @param enumName   the enum name, null returns null
105         * @return the enum, null if not found
106         */
107        public static <E extends Enum<E>> E getEnum(Class<E> enumClass, String enumName) {
108            if (enumName == null) {
109                return null;
110            }
111            try {
112                return Enum.valueOf(enumClass, enumName);
113            } catch (IllegalArgumentException ex) {
114                return null;
115            }
116        }
117    
118        /**
119         * <p>Creates a long bit vector representation of the given subset of an Enum.</p>
120         *
121         * <p>This generates a value that is usable by {@link EnumUtils#processBitVector}.</p>
122         *
123         * <p>Do not use this method if you have more than 64 values in your Enum, as this
124         * would create a value greater than a long can hold.</p>
125         *
126         * @param enumClass the class of the enum we are working with, not {@code null}
127         * @param values    the values we want to convert, not {@code null}
128         * @param <E>       the type of the enumeration
129         * @return a long whose binary value represents the given set of enum values.
130         * @throws NullPointerException if {@code enumClass} or {@code values} is {@code null}
131         * @throws IllegalArgumentException if {@code enumClass} is not an enum class or has more than 64 values
132         * @since 3.0.1
133         */
134        public static <E extends Enum<E>> long generateBitVector(Class<E> enumClass, Iterable<E> values) {
135            checkBitVectorable(enumClass);
136            Validate.notNull(values);
137            long total = 0;
138            for (E constant : values) {
139                total |= 1 << constant.ordinal();
140            }
141            return total;
142        }
143    
144        /**
145         * <p>Creates a long bit vector representation of the given array of Enum values.</p>
146         *
147         * <p>This generates a value that is usable by {@link EnumUtils#processBitVector}.</p>
148         *
149         * <p>Do not use this method if you have more than 64 values in your Enum, as this
150         * would create a value greater than a long can hold.</p>
151         *
152         * @param enumClass the class of the enum we are working with, not {@code null}
153         * @param values    the values we want to convert, not {@code null}
154         * @param <E>       the type of the enumeration
155         * @return a long whose binary value represents the given set of enum values.
156         * @throws NullPointerException if {@code enumClass} or {@code values} is {@code null}
157         * @throws IllegalArgumentException if {@code enumClass} is not an enum class or has more than 64 values
158         * @since 3.0.1
159         */
160        public static <E extends Enum<E>> long generateBitVector(Class<E> enumClass, E... values) {
161            Validate.noNullElements(values);
162            return generateBitVector(enumClass, Arrays.<E> asList(values));
163        }
164    
165        /**
166         * <p>Convert a long value created by {@link EnumUtils#generateBitVector} into the set of
167         * enum values that it represents.</p>
168         *
169         * <p>If you store this value, beware any changes to the enum that would affect ordinal values.</p>
170         * @param enumClass the class of the enum we are working with, not {@code null}
171         * @param value     the long value representation of a set of enum values
172         * @param <E>       the type of the enumeration
173         * @return a set of enum values
174         * @throws NullPointerException if {@code enumClass} is {@code null}
175         * @throws IllegalArgumentException if {@code enumClass} is not an enum class or has more than 64 values
176         * @since 3.0.1
177         */
178        public static <E extends Enum<E>> EnumSet<E> processBitVector(Class<E> enumClass, long value) {
179            final E[] constants = checkBitVectorable(enumClass).getEnumConstants();
180            final EnumSet<E> results = EnumSet.noneOf(enumClass);
181            for (E constant : constants) {
182                if ((value & 1 << constant.ordinal()) != 0) {
183                    results.add(constant);
184                }
185            }
186            return results;
187        }
188    
189        /**
190         * Validate that {@code enumClass} is compatible with representation in a {@code long}.
191         * @param <E> the type of the enumeration
192         * @param enumClass to check
193         * @return {@code enumClass}
194         * @throws NullPointerException if {@code enumClass} is {@code null}
195         * @throws IllegalArgumentException if {@code enumClass} is not an enum class or has more than 64 values
196         * @since 3.0.1
197         */
198        private static <E extends Enum<E>> Class<E> checkBitVectorable(Class<E> enumClass) {
199            Validate.notNull(enumClass, "EnumClass must be defined.");
200    
201            final E[] constants = enumClass.getEnumConstants();
202            Validate.isTrue(constants != null, "%s does not seem to be an Enum type", enumClass);
203            Validate.isTrue(constants.length <= Long.SIZE, "Cannot store %s %s values in %s bits", constants.length,
204                enumClass.getSimpleName(), Long.SIZE);
205    
206            return enumClass;
207        }
208    }