RFR: 8329760: Add indexOf(Predicate<? super E> filter) to java..util.List interface [v10]
Evemose
duke at openjdk.org
Fri Apr 19 15:39:12 UTC 2024
> **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 based on your suggestions.
>
> Thank you for considering this proposal.
>
> Best regards
>
> PS: In ...
Evemose has updated the pull request incrementally with two additional commits since the last revision:
- Merge remote-tracking branch 'origin/feature/indexOf-with-predicate' into feature/indexOf-with-predicate
# Conflicts:
# src/java.base/share/classes/java/util/LinkedList.java
# src/java.base/share/classes/java/util/ReverseOrderListView.java
# src/java.base/share/classes/java/util/Vector.java
# test/jdk/java/util/Spliterator/SpliteratorTraversingAndSplittingTest.java
- reverted code style changes
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/18639/files
- new: https://git.openjdk.org/jdk/pull/18639/files/97b9bff4..2c37ecef
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=18639&range=09
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=18639&range=08-09
Stats: 210 lines in 6 files changed: 11 ins; 44 del; 155 mod
Patch: https://git.openjdk.org/jdk/pull/18639.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/18639/head:pull/18639
PR: https://git.openjdk.org/jdk/pull/18639
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