    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
    015package org.apache.tapestry5.commons.util;
    016
    017import 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 */
    023public 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}