001    /*
002     * Copyright 2002-2004 the original author or authors.
003     *
004     * Licensed under the Apache License, Version 2.0 (the "License"); you may not
005     * use this file except in compliance with the License. You may obtain a copy of
006     * the License at
007     *
008     * http://www.apache.org/licenses/LICENSE-2.0
009     *
010     * Unless required by applicable law or agreed to in writing, software
011     * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
012     * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
013     * License for the specific language governing permissions and limitations under
014     * the License.
015     */
016    package org.springframework.rules.closure;
017    
018    import org.springframework.util.comparator.ComparableComparator;
019    import org.springframework.util.comparator.NullSafeComparator;
020    
021    /**
022     * Returns the maximum of two <code>Comparable</code> objects; with nulls regarded a 
023     * being less than non null.
024     *
025     * @author Keith Donald
026     */
027    public class Minimum extends AbstractBinaryClosure {
028    
029            private static final Minimum INSTANCE = new Minimum();
030        
031        private static final NullSafeComparator COMPARATOR = new NullSafeComparator(new ComparableComparator(), true);
032    
033            /**
034             * Returns the shared instance--this is possible as the default functor for
035             * this class is immutable and stateless.
036             *
037             * @return the shared instance
038             */
039            public static final BinaryClosure instance() {
040                    return INSTANCE;
041            }
042    
043            /**
044             * Return the minimum of two Comparable objects.
045             *
046             * @param comparable1
047             *            the first comparable
048             * @param comparable2
049             *            the second comparable
050             * @return the minimum
051             */
052            public Object call(Object comparable1, Object comparable2) {
053                    int result = COMPARATOR.compare(comparable1,
054                                    comparable2);
055                    if (result < 0) {
056                            return comparable1;
057                    }
058                    else if (result > 0) {
059                            return comparable2;
060                    }
061                    return comparable1;
062            }
063    
064            public String toString() {
065                    return "min(arg1, arg2)";
066            }
067    
068    }