    001    // Copyright 2006 The Apache Software Foundation
    002    //
    003    // Licensed under the Apache License, Version 2.0 (the "License");
    004    // you may not use this file except in compliance with the License.
    005    // You may obtain a copy of the License at
    006    //
    007    //     http://www.apache.org/licenses/LICENSE-2.0
    008    //
    009    // Unless required by applicable law or agreed to in writing, software
    010    // distributed under the License is distributed on an "AS IS" BASIS,
    011    // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    012    // See the License for the specific language governing permissions and
    013    // limitations under the License.
    014
    015    package org.apache.tapestry5.internal.util;
    016
    017    import java.util.Iterator;
    018
    019    /**
    020     * Represents a sequence of integer values, either ascending or descending. The sequence is always inclusive (of the
    021     * finish value).
    022     */
    023    public final class IntegerRange implements Iterable<Integer>
    024    {
    025        private final int start;
    026
    027        private final int finish;
    028
    029        private class RangeIterator implements Iterator<Integer>
    030        {
    031            private final int increment;
    032
    033            private int value = start;
    034
    035            private boolean hasNext = true;
    036
    037            RangeIterator()
    038            {
    039                increment = start < finish ? +1 : -1;
    040            }
    041
    042            public boolean hasNext()
    043            {
    044                return hasNext;
    045            }
    046
    047            public Integer next()
    048            {
    049                if (!hasNext) throw new IllegalStateException();
    050
    051                int result = value;
    052
    053                hasNext = value != finish;
    054
    055                value += increment;
    056
    057                return result;
    058            }
    059
    060            public void remove()
    061            {
    062                throw new UnsupportedOperationException();
    063            }
    064
    065        }
    066
    067        public IntegerRange(final int start, final int finish)
    068        {
    069            this.start = start;
    070            this.finish = finish;
    071        }
    072
    073        public int getFinish()
    074        {
    075            return finish;
    076        }
    077
    078        public int getStart()
    079        {
    080            return start;
    081        }
    082
    083        @Override
    084        public String toString()
    085        {
    086            return String.format("%d..%d", start, finish);
    087        }
    088
    089        /**
    090         * The main puprose of a range object is to produce an Iterator. Since IntegerRange is iterable, it is useful with
    091         * the Tapestry Loop component, but also with the Java for loop!
    092         */
    093        public Iterator<Integer> iterator()
    094        {
    095            return new RangeIterator();
    096        }
    097
    098        @Override
    099        public int hashCode()
    100        {
    101            final int PRIME = 31;
    102
    103            int result = PRIME + finish;
    104
    105            result = PRIME * result + start;
    106
    107            return result;
    108        }
    109
    110        /**
    111         * Returns true if the other object is an IntegerRange with the same start and finish values.
    112         */
    113        @Override
    114        public boolean equals(Object obj)
    115        {
    116            if (this == obj) return true;
    117            if (obj == null) return false;
    118            if (getClass() != obj.getClass()) return false;
    119            final IntegerRange other = (IntegerRange) obj;
    120            if (finish != other.finish) return false;
    121
    122            return start == other.start;
    123        }
    124
    125    }