On Tue, 23 Apr 2024 13:51:54 GMT, Evemose <d...@openjdk.org> wrote:
>> **Subject**
>> Addition of Predicate-based `indexOf` and `lastIndexOf` methods to
>> `java.util.List`
>>
>> **Motivation**
>> The motivation behind this proposal is to enhance the functionality of the
>> `List` interface by providing a more flexible way to find the index of an
>> element. Currently, the `indexOf` and `lastIndexOf` methods only accept an
>> object as a parameter. This limits the flexibility of these methods as they
>> can only find the index of exact object matches.
>>
>> The proposed methods would accept a `Predicate` as a parameter, allowing
>> users to define a condition that the desired element must meet. This would
>> provide a more flexible and powerful way to find the index of an element in
>> a list.
>>
>> Here is a brief overview of the changes made in this pull request:
>>
>> 1. Added the `indexOf(Predicate<? super E> filter)` method to the `List`
>> interface.
>> 2. Added the `lastIndexOf(Predicate<? super E> filter)` method to the `List`
>> interface.
>> 3. Implemented these methods in all non-abstract classes that implement the
>> `List` interface.
>>
>> The changes have been thoroughly tested to ensure they work as expected and
>> do not introduce any regressions. The test cases cover a variety of
>> scenarios to ensure the robustness of the implementation.
>>
>> For example, consider the following test case:
>>
>> List<String> list = new ArrayList<>();
>> list.add("Object one");
>> list.add("NotObject two");
>> list.add("NotObject three");
>>
>> int index1 = list.indexOf(s -> s.contains("ct t"));
>> System.out.println(index1); // Expected output: 1
>> int index2 = list.lastIndexOf(s -> s.startsWith("NotObject"));
>> System.out.println(index2); // Expected output: 2
>>
>>
>> Currently, to achieve the same result, we would have to use a more verbose
>> approach:
>>
>> int index1 = IntStream.range(0, list.size())
>> .filter(i -> list.get(i).contains("ct t"))
>> .findFirst()
>> .orElse(-1);
>> System.out.println(index1); // Output: 1
>> int index2 = IntStream.range(0, list.size())
>> .filter(i -> list.get(i).startsWith("NotObject"))
>> .reduce((first, second) -> second)
>> .orElse(-1);
>> System.out.println(index2); // Output: 2
>>
>>
>> I believe these additions would greatly enhance the functionality and
>> flexibility of the `List` interface, making it more powerful and
>> user-friendly. I look forward to your feedback and am open to making any
>> necessary changes bas...
>
> Evemose has updated the pull request incrementally with three additional
> commits since the last revision:
>
> - Added Objects import to sun List
> - Replaced on-demand import in com.sun....List
> - added non-null assertions
src/java.base/share/classes/java/util/LinkedList.java line 1507:
> 1505:
> 1506: public int findLastIndex(Predicate<? super E> filter) {
> 1507: return rlist.findLastIndex(filter);
Hmm, this view is supposed to be reversed... so last and first need a swap.
This is a bug in the current codebase, a good bug to fix indeed.
-------------
PR Review Comment: https://git.openjdk.org/jdk/pull/18639#discussion_r1573456708
