    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.collections4.functors;
    018
    019import java.io.Serializable;
    020import java.util.Map;
    021
    022import org.apache.commons.collections4.Closure;
    023import org.apache.commons.collections4.Predicate;
    024
    025/**
    026 * Closure implementation calls the closure whose predicate returns true,
    027 * like a switch statement.
    028 *
    029 * @since 3.0
    030 */
    031public class SwitchClosure<E> implements Closure<E>, Serializable {
    032
    033    /** Serial version UID */
    034    private static final long serialVersionUID = 3518477308466486130L;
    035
    036    /** The tests to consider */
    037    private final Predicate<? super E>[] iPredicates;
    038    /** The matching closures to call */
    039    private final Closure<? super E>[] iClosures;
    040    /** The default closure to call if no tests match */
    041    private final Closure<? super E> iDefault;
    042
    043    /**
    044     * Factory method that performs validation and copies the parameter arrays.
    045     *
    046     * @param <E> the type that the closure acts on
    047     * @param predicates  array of predicates, cloned, no nulls
    048     * @param closures  matching array of closures, cloned, no nulls
    049     * @param defaultClosure  the closure to use if no match, null means nop
    050     * @return the <code>chained</code> closure
    051     * @throws NullPointerException if array is null
    052     * @throws NullPointerException if any element in the array is null
    053     * @throws IllegalArgumentException if the array lengths of predicates and closures do not match
    054     */
    055    @SuppressWarnings("unchecked")
    056    public static <E> Closure<E> switchClosure(final Predicate<? super E>[] predicates,
    057                                               final Closure<? super E>[] closures,
    058                                               final Closure<? super E> defaultClosure) {
    059        FunctorUtils.validate(predicates);
    060        FunctorUtils.validate(closures);
    061        if (predicates.length != closures.length) {
    062            throw new IllegalArgumentException("The predicate and closure arrays must be the same size");
    063        }
    064        if (predicates.length == 0) {
    065            return (Closure<E>) (defaultClosure == null ? NOPClosure.<E>nopClosure(): defaultClosure);
    066        }
    067        return new SwitchClosure<>(predicates, closures, defaultClosure);
    068    }
    069
    070    /**
    071     * Create a new Closure that calls one of the closures depending
    072     * on the predicates.
    073     * <p>
    074     * The Map consists of Predicate keys and Closure values. A closure
    075     * is called if its matching predicate returns true. Each predicate is evaluated
    076     * until one returns true. If no predicates evaluate to true, the default
    077     * closure is called. The default closure is set in the map with a
    078     * null key. The ordering is that of the iterator() method on the entryset
    079     * collection of the map.
    080     *
    081     * @param <E> the type that the closure acts on
    082     * @param predicatesAndClosures  a map of predicates to closures
    083     * @return the <code>switch</code> closure
    084     * @throws NullPointerException if the map is null
    085     * @throws NullPointerException if any closure in the map is null
    086     * @throws ClassCastException  if the map elements are of the wrong type
    087     */
    088    @SuppressWarnings("unchecked")
    089    public static <E> Closure<E> switchClosure(final Map<Predicate<E>, Closure<E>> predicatesAndClosures) {
    090        if (predicatesAndClosures == null) {
    091            throw new NullPointerException("The predicate and closure map must not be null");
    092        }
    093        // convert to array like this to guarantee iterator() ordering
    094        final Closure<? super E> defaultClosure = predicatesAndClosures.remove(null);
    095        final int size = predicatesAndClosures.size();
    096        if (size == 0) {
    097            return (Closure<E>) (defaultClosure == null ? NOPClosure.<E>nopClosure() : defaultClosure);
    098        }
    099        final Closure<E>[] closures = new Closure[size];
    100        final Predicate<E>[] preds = new Predicate[size];
    101        int i = 0;
    102        for (final Map.Entry<Predicate<E>, Closure<E>> entry : predicatesAndClosures.entrySet()) {
    103            preds[i] = entry.getKey();
    104            closures[i] = entry.getValue();
    105            i++;
    106        }
    107        return new SwitchClosure<>(false, preds, closures, defaultClosure);
    108    }
    109
    110    /**
    111     * Hidden constructor for the use by the static factory methods.
    112     *
    113     * @param clone  if {@code true} the input arguments will be cloned
    114     * @param predicates  array of predicates, no nulls
    115     * @param closures  matching array of closures, no nulls
    116     * @param defaultClosure  the closure to use if no match, null means nop
    117     */
    118    @SuppressWarnings("unchecked")
    119    private SwitchClosure(final boolean clone, final Predicate<? super E>[] predicates,
    120                          final Closure<? super E>[] closures, final Closure<? super E> defaultClosure) {
    121        super();
    122        iPredicates = clone ? FunctorUtils.copy(predicates) : predicates;
    123        iClosures = clone ? FunctorUtils.copy(closures) : closures;
    124        iDefault = (Closure<? super E>) (defaultClosure == null ? NOPClosure.<E>nopClosure() : defaultClosure);
    125    }
    126
    127    /**
    128     * Constructor that performs no validation.
    129     * Use <code>switchClosure</code> if you want that.
    130     *
    131     * @param predicates  array of predicates, cloned, no nulls
    132     * @param closures  matching array of closures, cloned, no nulls
    133     * @param defaultClosure  the closure to use if no match, null means nop
    134     */
    135    public SwitchClosure(final Predicate<? super E>[] predicates, final Closure<? super E>[] closures,
    136                         final Closure<? super E> defaultClosure) {
    137        this(true, predicates, closures, defaultClosure);
    138    }
    139
    140    /**
    141     * Executes the closure whose matching predicate returns true
    142     *
    143     * @param input  the input object
    144     */
    145    @Override
    146    public void execute(final E input) {
    147        for (int i = 0; i < iPredicates.length; i++) {
    148            if (iPredicates[i].evaluate(input) == true) {
    149                iClosures[i].execute(input);
    150                return;
    151            }
    152        }
    153        iDefault.execute(input);
    154    }
    155
    156    /**
    157     * Gets the predicates.
    158     *
    159     * @return a copy of the predicates
    160     * @since 3.1
    161     */
    162    public Predicate<? super E>[] getPredicates() {
    163        return FunctorUtils.<E>copy(iPredicates);
    164    }
    165
    166    /**
    167     * Gets the closures.
    168     *
    169     * @return a copy of the closures
    170     * @since 3.1
    171     */
    172    public Closure<? super E>[] getClosures() {
    173        return FunctorUtils.<E>copy(iClosures);
    174    }
    175
    176    /**
    177     * Gets the default closure.
    178     *
    179     * @return the default closure
    180     * @since 3.1
    181     */
    182    public Closure<? super E> getDefaultClosure() {
    183        return iDefault;
    184    }
    185
    186}