**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
-------------
Commit messages:
- did some renaming of internal methods utilized by findIndex
- fixed ReverseOrderLinkedListView
- fixed javadocs in List and ArrayList
- Merge remote-tracking branch 'origin/feature/indexOf-with-predicate' into
feature/indexOf-with-predicate
- Removed unused import in AbstractList
- Also moved to List interface
- Moved from AbstractList
- Removed implementation from AbstractList, moving it to List
- Renamed indexOf(Predicate) and lastIndexOf(Predicate) to
findIndex(Predicate) and findLastIndex(Predicate) respectively
- Merge remote-tracking branch 'origin/feature/indexOf-with-predicate' into
feature/indexOf-with-predicate
- ... and 25 more: https://git.openjdk.org/jdk/compare/16576b87...025bcf39
Changes: https://git.openjdk.org/jdk/pull/18639/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18639&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8329760
Stats: 882 lines in 13 files changed: 570 ins; 47 del; 265 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
