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Date: Tue, 5 Mar 2013 11:31:46 +0100
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Subject: Re: svn commit: r1451914 -
 /commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
From: Benedikt Ritter <britter@apache.org>
To: Commons Developers List <dev@commons.apache.org>
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2013/3/3 Benedikt Ritter <britter@apache.org>

>
>
>
> 2013/3/2 Thomas Neidhart <thomas.neidhart@gmail.com>
>
>> On 03/02/2013 07:33 PM, Benedikt Ritter wrote:
>> > 2013/3/2 <tn@apache.org>
>> >
>> >> Author: tn
>> >> Date: Sat Mar  2 18:12:46 2013
>> >> New Revision: 1451914
>> >>
>> >> URL: http://svn.apache.org/r1451914
>> >> Log:
>> >> [COLLECTIONS-366] Added ListUtils.range methods.
>> >>
>> >> Modified:
>> >>
>> >>
>> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
>> >>
>> >> Modified:
>> >>
>> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
>> >> URL:
>> >>
>> http://svn.apache.org/viewvc/commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java?rev=1451914&r1=1451913&r2=1451914&view=diff
>> >>
>> >>
>> ==============================================================================
>> >> ---
>> >>
>> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
>> >> (original)
>> >> +++
>> >>
>> commons/proper/collections/trunk/src/main/java/org/apache/commons/collections/ListUtils.java
>> >> Sat Mar  2 18:12:46 2013
>> >> @@ -507,6 +507,9 @@ public class ListUtils {
>> >>          return -1;
>> >>      }
>> >>
>> >> +    // partition
>> >> +
>> >>
>>  //-------------------------------------------------------------------------
>> >> +
>> >>      /**
>> >>       * Returns consecutive {@link List#subList(int, int) sublists} of
>> a
>> >>       * list, each of the same size (the final list may be smaller).
>> For
>> >> example,
>> >> @@ -579,4 +582,99 @@ public class ListUtils {
>> >>              return list.isEmpty();
>> >>          }
>> >>      }
>> >> +
>> >> +    // range
>> >> +
>> >>
>>  //-------------------------------------------------------------------------
>> >> +
>> >> +    /**
>> >> +     * Returns an unmodifiable List of integers in the range [0, size
>> -
>> >> 1].
>> >> +     * <p>
>> >> +     * The returned list does not store the actual numbers, but checks
>> >> +     * if a given number would be contained in the defined range. A
>> call
>> >> +     * to {@link #contains(Object)} is very fast - O(1).
>> >> +     *
>> >> +     * @see #range(int,int)
>> >> +     *
>> >> +     * @param size  the size of the returned list
>> >> +     * @return an unmodifiable list of integers in the range [0, size
>> - 1]
>> >> +     * @throws IllegalArgumentException if from &gt; to
>> >> +     * @since 4.0
>> >> +     */
>> >> +    public static List<Integer> range(final int size) {
>> >> +        return range(0, size - 1);
>> >> +    }
>> >> +
>> >> +    /**
>> >> +     * Returns an unmodifiable List of integers in the range [from,
>> to].
>> >> +     * <p>
>> >> +     * The returned list does not store the actual numbers, but checks
>> >> +     * if a given number would be contained in the defined range. A
>> call
>> >> +     * to {@link #contains(Object)} is very fast - O(1).
>> >> +     * <p>
>> >> +     * The bounds of the range are allowed to be negative.
>> >> +     *
>> >> +     * @param from  the start of the range
>> >> +     * @param to  the end of the range (inclusive)
>> >> +     * @return an unmodifiable list of integers in the specified range
>> >> +     * @throws IllegalArgumentException if from &gt; to
>> >> +     * @since 4.0
>> >> +     */
>> >> +    public static List<Integer> range(final int from, final int to) {
>> >> +        return ListUtils.unmodifiableList(new RangeList(from, to));
>> >> +    }
>> >> +
>> >> +    /**
>> >> +     * Provides a memory-efficient implementation of a fixed range
>> list.
>> >> +     * @since 4.0
>> >> +     */
>> >> +    private static final class RangeList extends
>> AbstractList<Integer> {
>> >> +        private final int from;
>> >> +        private final int to;
>> >> +
>> >> +        /**
>> >> +         * Creates a list of integers with a given range, inclusive.
>> >> +         *
>> >> +         * @param from  the start of the range
>> >> +         * @param to  the end of the range (inclusive)
>> >> +         * @throws IllegalArgumentException if from &gt; to
>> >> +         */
>> >> +        private RangeList(final int from, final int to) {
>> >> +            if (to < from) {
>> >> +                throw new IllegalArgumentException("from(" + from +
>> ") >
>> >> to(" + to + ")");
>> >> +            }
>> >> +
>> >> +            this.from = from;
>> >> +            this.to = to;
>> >> +        }
>> >> +
>> >> +        public int size() {
>> >> +            return to - from + 1;
>> >> +        }
>> >> +
>> >> +        public Integer get(final int index) {
>> >> +            final int sz = size();
>> >> +            if (index >= sz || index < 0) {
>> >> +                throw new IndexOutOfBoundsException("Index: " + index
>> +
>> >> ", Size: " + sz);
>> >> +            }
>> >> +            return Integer.valueOf(index + from);
>> >> +        }
>> >> +
>> >> +        public int indexOf(Object o) {
>> >> +            if (o instanceof Number) {
>> >
>> > +                final int value = ((Number) o).intValue();
>> >>
>> >
>> > Why do we cast to Number instead of Integer?
>> >
>> > With this implementation the following will fail:
>> >
>> >     public void testRange() {
>> >         List<Integer> range = ListUtils.range(0, 1);
>> >         assertFalse(range.contains(Double.valueOf(1.2d)));
>> >     }
>>
>> because it was like this in the original patch.
>> I looked at it and found it ok, but it has to be documented in the
>> contains method that any number passes as argument is converted to int,
>> which I forgot (still need to commit the unit tests).
>>
>>
> Okay, but even if this was documented it feels strange that 1.2 is
> contained in [0,1] or am I missing something here?
>

Thomas, can you please comment on this? I don't understand why 1.2 should
be contained in [0,1] or is this a result of the incomplete implementation
and will be changed?

TIA!
Benedikt


> Would be nice to have some unit tests in place.
>
>
>> Right now, the returned list is not a full-blown Range implementation,
>> but this maybe a useful addition in the future.
>>
>
> No questions about that! As I commented in the issue, I like this feature!
> :)
>
>
>>
>> Thomas
>>
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>>
>
>
> --
> http://people.apache.org/~britter/
> http://www.systemoutprintln.de/
> http://twitter.com/BenediktRitter
> http://github.com/britter
>


-- 
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