Name: akC97680 Date: 12/22/99



The javadoc spec for java.util.Arrays.binarySearch(Object[], Object) states:
----------- begin javadoc -----------------

public static int binarySearch(Object[] a,
                               Object key)

     Searches the specified array for the specified object using the binary
     search algorithm. The array must be sorted into ascending order according
                       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     to the natural ordering of its elements (as by Sort(Object[]), above) prior
     to making this call. If it is not sorted, the results are undefined. If the
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
     array contains multiple elements equal to the specified object, there is no
     guarantee which one will be found.

-- skip

     Throws:
         ClassCastException - if the array contains elements that are not
                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         mutually comparable (for example, strings and integers), or the search
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
         key in not mutually comparable with the elements of the array.

----------- end javadoc -------------------

The ambiguity shows up in the case of array containing mutually incomparable
elements. For example, as javadoc says, consider case of search of an Integer
object in the array containing strings and integers. On one hand, the array must
be sorted prior to search, if it is not so, result of execution will be
undefined. On other hand, this array cannot be sorted as it does contain
incomparable elements: call to sort will throw ClassCastException. The problem
is what one should expect from the binarySearch(Object[], Object) if tries to
search Integer object in this array?

Current implementation sometimes throws ClassCastException, sometimes does
not (depending on elements' location and values).

Also there is the JCK test, that fails because of this reason.
api/java_util/Arrays/TestDesc.html#Arrays.binarySearch(Object[],Object)_fail

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