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 */
017package org.apache.commons.functor.core.collection;
018
019import java.lang.reflect.Array;
020import java.util.Collection;
021
022import org.apache.commons.functor.Function;
023import org.apache.commons.lang3.Validate;
024
025/**
026 * Returns the size of the specified Collection, or the length
027 * of the specified array or String.
028 *
029 * @param <A> the function argument type.
030 * @version $Revision: 1537901 $ $Date: 2013-11-01 12:30:19 +0100 (Fr, 01 Nov 2013) $
031 */
032public final class Size<A> implements Function<A, Integer> {
033
034    /**
035     * A static {@code Size} instance reference.
036     */
037    private static final Size<Object> INSTANCE = new Size<Object>();
038
039    // constructor
040    // ------------------------------------------------------------------------
041    /**
042     * Create a new Size.
043     */
044    public Size() { }
045
046    /**
047     * {@inheritDoc}
048     */
049    public Integer evaluate(Object obj) {
050        Validate.notNull(obj, "Argument must not be null");
051        if (obj instanceof Collection<?>) {
052            return evaluate((Collection<?>) obj);
053        }
054        if (obj instanceof String) {
055            return evaluate((String) obj);
056        }
057        if (obj.getClass().isArray()) {
058            return evaluateArray(obj);
059        }
060        throw new IllegalArgumentException("Expected Collection, String or Array, found " + obj);
061    }
062
063    /**
064     * {@inheritDoc}
065     */
066    @Override
067    public boolean equals(Object that) {
068        return that instanceof Size<?>;
069    }
070
071    /**
072     * {@inheritDoc}
073     */
074    @Override
075    public int hashCode() {
076        return "Size".hashCode();
077    }
078
079    /**
080     * {@inheritDoc}
081     */
082    @Override
083    public String toString() {
084        return "Size()";
085    }
086
087    /**
088     * Get a Size instance.
089     * @return Size
090     */
091    public static Size<Object> instance() {
092        return INSTANCE;
093    }
094
095    /**
096     * Evaluate a Collection.
097     * @param col to evaluate
098     * @return Integer
099     */
100    private Integer evaluate(Collection<?> col) {
101        return Integer.valueOf(col.size());
102    }
103
104    /**
105     * Evaluate a String.
106     * @param str to evaluate
107     * @return Integer
108     */
109    private Integer evaluate(String str) {
110        return Integer.valueOf(str.length());
111    }
112
113    /**
114     * Evaluate an array.
115     * @param array to evaluate
116     * @return Integer
117     */
118    private Integer evaluateArray(Object array) {
119        return Integer.valueOf(Array.getLength(array));
120    }
121
122}