[jira] [Commented] (LANG-536) Add isSorted() to ArrayUtils

["Duncan Jones (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/LANG-536?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14170872#comment-14170872 ] 

Duncan Jones commented on LANG-536:
-----------------------------------

Thanks for the patch, James. It looks good, but I think it requires a few changes before it can be committed.

I'm concerned about the conversion of the primitive arrays to object arrays. I can see the benefits in terms of code re-use, but I think we should be implementing each method individually without converting the arrays (for performance reasons). We should still make use of the {{compareTo()}} method provided in the equivalent object class to perform the comparison though.

The Javadoc comments need to be encased in {{<p></p>}} as per our [developer guidelines|http://commons.apache.org/proper/commons-lang/developerguide.html], also {{@code}} should be used where applicable.

Your test for the {{isSorted(T[] a, Comparator<? super T> c)}} method might be improved by specifying a more interesting comparator. I.e. something that doesn't use natural ordering. This ensures the method isn't accidentally ignoring the supplied comparator.


> Add isSorted() to ArrayUtils
> ----------------------------
>
>                 Key: LANG-536
>                 URL: https://issues.apache.org/jira/browse/LANG-536
>             Project: Commons Lang
>          Issue Type: New Feature
>          Components: lang.*
>            Reporter: Sergei Ivanov
>            Priority: Minor
>             Fix For: Review Patch
>
>         Attachments: LANG-536.patch
>
>
> In my unit tests I often need to verify that an array is correctly sorted.
> In order to achieve this, I've got two helper methods as follows.
> Is it possible to integrate these methods into ArrayUtils?
> {code}
>     /**
>      * Checks that the specified array of objects is in an ascending order
>      * according to the specified comparator.  All elements in the array must be
>      * <i>mutually comparable</i> by the specified comparator (that is,
>      * <tt>c.compare(e1, e2)</tt> must not throw a <tt>ClassCastException</tt>
>      * for any elements <tt>e1</tt> and <tt>e2</tt> in the array).
>      *
>      * @param a the array to be checked.
>      * @param c the comparator to determine the order of the array.  A
>      * <tt>null</tt> value indicates that the elements'
>      * {@linkplain Comparable natural ordering} should be used.
>      * @return {@code true}, if the array is sorted; {@code false}, otherwise.
>      * @throws ClassCastException if the array contains elements that are
>      * not <i>mutually comparable</i> using the specified comparator.
>      */
>     public static <T> boolean isSorted(final T[] a, final Comparator<? super T> c) {
>         if (a.length <= 1) {
>             // Empty or singleton arrays are always sorted
>             return true;
>         }
>         // Otherwise, check that every element is not smaller than the previous
>         T previous = a[0];
>         for (int i = 1, n = a.length; i < n; i++) {
>             final T current = a[i];
>             if (c.compare(previous, current) > 0) {
>                 return false;
>             }
>             previous = current;
>         }
>         return true;
>     }
>     /**
>      * Checks that the specified array of objects is in an ascending order,
>      * according to the {@linkplain Comparable natural ordering} of its elements.
>      * All elements in the array must implement the {@link Comparable} interface.
>      * Furthermore, all elements in the array must be <i>mutually comparable</i>
>      * (that is, <tt>e1.compareTo(e2)</tt> must not throw a <tt>ClassCastException</tt>
>      * for any elements <tt>e1</tt> and <tt>e2</tt> in the array).
>      *
>      * @param a the array to be checked.
>      * @return {@code true}, if the array is sorted; {@code false}, otherwise.
>      * @throws ClassCastException if the array contains elements that are not
>      * <i>mutually comparable</i> (for example, strings and integers).
>      */
>     @SuppressWarnings({"unchecked"})
>     public static <T> boolean isSorted(final T[] a) {
>         if (a.length <= 1) {
>             // Empty or singleton arrays are always sorted
>             return true;
>         }
>         // Otherwise, check that every element is not smaller than the previous
>         T previous = a[0];
>         for (int i = 1, n = a.length; i < n; i++) {
>             final T current = a[i];
>             if (((Comparable<? super T>) previous).compareTo(previous) > 0) {
>                 return false;
>             }
>             previous = current;
>         }
>         return true;
>     }
> {code}



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