Add findDuplicates Method to ListUtils with Comprehensive Test Cases #537

hemanth0525 · 2024-08-31T19:29:54Z

Summary

This pull request introduces the findDuplicates method to the ListUtils class, a feature designed to enhance the functionality of list operations by providing a straightforward way to detect duplicate elements.

Why This Change?

In many software development scenarios, detecting duplicates within a list is a common task. This functionality is essential for tasks such as data validation, cleaning, and processing. Instead of requiring developers to implement custom solutions or rely on third-party libraries, this method integrates seamlessly into the ListUtils class, offering a reliable and efficient way to handle duplicate detection.

How This Change is Useful

Efficiency:
- The findDuplicates method is implemented with optimal performance in mind, ensuring that duplicate detection is handled efficiently even for large lists.
Simplification:
- Provides a single, reusable method for duplicate detection, reducing the need for repetitive code across different projects.
Versatility:
- Handles a variety of scenarios, including lists with different types of elements, empty lists, and lists with no duplicates.

Example Usage

List<Integer> numbers = Arrays.asList(1, 2, 3, 2, 4, 5, 3);
List<Integer> duplicates = ListUtils.findDuplicates(numbers); // [2, 3]

garydgregory

Since the result is effectively a set and the input does not have to be restricted to a list, it would be better to do this IMO:

    public static <E> Set<E> duplicates(final Collection<E> list) {
        final HashSet<E> dups = new HashSet<>();
        final HashSet<E> set = new HashSet<>();
        for (E e : list) {
            (set.contains(e) ? dups : set).add(e);
        }
        return dups;
    }

and put it in CollectionUtils probably.

hemanth0525 · 2024-09-01T04:23:19Z

Since the result is effectively a set and the input does not have to be restricted to a list, it would be better to do this IMO:

    public static <E> Set<E> duplicates(final Collection<E> list) {
        final HashSet<E> dups = new HashSet<>();
        final HashSet<E> set = new HashSet<>();
        for (E e : list) {
            (set.contains(e) ? dups : set).add(e);
        }
        return dups;
    }

and put it in CollectionUtils probably.

Thanks for the feedback. The ListUtils implementation is tailored for List<E>, preserving the order of elements and identifying duplicates where the sequence matters. This approach is particularly useful in scenarios such as:

Preserving Order: When the sequence of elements is important, such as in order-sensitive algorithms or data processing tasks.
List-Specific APIs: When working with APIs that return or expect List, ensuring that the utility aligns with the data structure's inherent properties.
Performance Considerations: In cases where developers need efficient duplicate detection while maintaining the list's order, which can be crucial in performance-sensitive applications.

Keeping this method in ListUtils supports these specific needs and maintains consistency for developers working with ordered collections.

src/main/java/org/apache/commons/collections4/ListUtils.java

garydgregory

See my comments. The input can still be

src/main/java/org/apache/commons/collections4/ListUtils.java

src/test/java/org/apache/commons/collections4/ListUtilsTest.java

garydgregory · 2024-09-01T15:04:28Z

Hello @hemanth0525

Please see git master for:

Add CollectionUtils.duplicateList(Collection)
Add CollectionUtils.duplicateSequencedSet(Collection)
Add CollectionUtils.duplicateSet(Collection)

You are credited in changes.xml

Are there tests or functionality we could provide specific to ListUtils?

I believe that this PR's new ListUtils method is now the same in functionality as CollectionUtils.duplicateList(Collection<E>)

Note that this PR is still failing. Run 'mvn' by itself before you push to catch all build errors.

TY!

hemanth0525 · 2024-09-01T17:24:07Z

hello @garydgregory,

TY !

I guess all the change requests are done.

i have run mvn locally and build success !

hemanth0525 · 2024-09-02T14:02:13Z

hello @garydgregory
is this PR ready to merge ?

garydgregory · 2024-09-02T14:02:51Z

src/main/java/org/apache/commons/collections4/ListUtils.java

+     * @since 4.5.0-M3
+     */
+    public static <E> List<E> findDuplicates(final List<E> list) {
+        Objects.requireNonNull(list, "The input list must not be null.");


@hemanth0525

If you replace the body of this (git master) method with:

return IterableUtils.duplicateList(list);

You'll find that all tests pass.
So I don't think we need this method in this class.

u mean from CollectionUtils ?

if yes, I have done it. So yeah utilizing the other function to help list functionalities.

garydgregory · 2024-09-02T15:22:54Z

src/main/java/org/apache/commons/collections4/ListUtils.java

+     * @since 4.5.0-M3
+     */
+    public static <E> List<E> findDuplicates(final List<E> list) {
+        return CollectionUtils.duplicateList(list);


If you rebase on git master, you'll find this method in 'IterableUtils'.

Bumps [org.easymock:easymock](https://github.com/easymock/easymock) from 5.3.0 to 5.4.0. - [Release notes](https://github.com/easymock/easymock/releases) - [Changelog](https://github.com/easymock/easymock/blob/master/ReleaseNotes.md) - [Commits](easymock/easymock@easymock-5.3.0...easymock-5.4.0) --- updated-dependencies: - dependency-name: org.easymock:easymock dependency-type: direct:development update-type: version-update:semver-minor ... Signed-off-by: dependabot[bot] <[email protected]>

Javadoc

Bags instead of custom Maps

- Add TreeBag.TreeBag(Iterable)

- Close HTML tags - Reduce whitespace

Objects.requireNonNull()

…25/commons-collections into feature/findDuplicates

…into feature/findDuplicates

hemanth0525 · 2024-09-02T16:13:41Z

Oh Yeah !!
Done!!

garydgregory · 2024-09-03T12:32:58Z

Hello @hemanth0525
If all the new method does is delegate to IterableUtils.duplicateList(), it is unnecessary. The tests in this PR may cover use cases not in IterableUtilsTest.

hemanth0525 · 2024-09-03T15:28:37Z

@garydgregory Okay so what u want me to do in this case ?

garydgregory · 2024-09-03T16:26:11Z

I would either close the PR or update it if there are missing use cases in IterableUtilsTest (if yes, then also remove the new method from this PR).

hemanth0525 · 2024-09-03T16:31:40Z

you can update

garydgregory · 2024-09-03T17:00:14Z

I don't understand what you mean.

hemanth0525 · 2024-09-03T17:24:49Z

sorry !
I will look for the use cases.

Suggested Improvement
For the duplicateList method, it might be more appropriate to call duplicateSequencedSet instead of duplicateSet. Since the method returns a List, preserving the order of elements is often expected or desirable. By using duplicateSequencedSet, we can ensure that the order of duplicate elements is maintained, providing a more intuitive and consistent behavior for users of this method.

    /**
     * Finds and returns the List of duplicate elements in the given collection.
     *
     * @param <E> the type of elements in the collection.
     * @param iterable the list to test, must not be null.
     * @return the set of duplicate elements, may be empty.
     * @since 4.5.0-M3
     */
    public static <E> List<E> duplicateList(final Iterable<E> iterable) {
        return new ArrayList<>(duplicateSet(iterable));
    }

Shall i make this update ?

garydgregory · 2024-09-03T17:46:23Z

@hemanth0525

In git master, we now make sure IterableUtils.duplicateList() has predictable order in its
result.

Add testDuplicateListMultipleDuplicatesInDequeReverse()
Add testDuplicateListMultipleDuplicatesInListReverse()
If you do not care about order, you can use IterableUtils.duplicateSet()

hemanth0525 · 2024-09-03T17:50:05Z

@garydgregory I just did that and thought of commiting...........

- Mixed element types - Nested collections - Custom objects - Large-scale data - Immutable collections

…ctions into feature/findDuplicates

hemanth0525 · 2024-09-04T18:41:03Z

Hello @garydgregory,

I have added several diverse test cases to IterableUtilsTest.java. Kindly review them.

hemanth0525 · 2024-09-07T15:47:25Z

update on this PR ?

garydgregory · 2024-09-08T15:36:43Z

Hello @hemanth0525

Does the PR now provide additional code coverage? You can tell when you run "mvn clean install site" and you look at the JaCoCo report.

Gary

- Mixed element types - Nested collections - Custom objects - Large-scale data - Immutable collections

…25/commons-collections into feature/findDuplicates

hemanth0525 · 2024-09-08T19:34:54Z

i dont see any additional code coverage

hemanth0525 · 2024-09-11T06:27:02Z

this PR started to provide functionalities to find duplicates to list which u have implemented in IterableUtils for all collections. so ig lets close this PR now

Add findDuplicates method to ListUtils with comprehensive test cases

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hemanth0525 added 3 commits September 1, 2024 14:24

findDuplicates

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updated tests

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Update tests

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hemanth0525 added 3 commits September 1, 2024 21:32

Merge branch 'apache:master' into master

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Merge branch 'apache:master' into feature/findDuplicates

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Add findDuplicates

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Merge branch 'apache:master' into feature/findDuplicates

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garydgregory reviewed Sep 2, 2024

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Add findDuplicates

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hemanth0525 and others added 12 commits September 2, 2024 21:25

Add findDuplicates

9197ae3

Bump org.easymock:easymock from 5.3.0 to 5.4.0 #521

a465792

Whitespace

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Use Java 8's Map.getOrDefault()

ff20df6

Javadoc

Reimplement the package-private CollectionUtils.CardinalityHelper using

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Bags instead of custom Maps

Add HashBag.HashBag(Iterable)

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- Add TreeBag.TreeBag(Iterable)

[COLLECTIONS-858] CartesianProductIterator

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Add CartesianProductIterator #509

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Javadoc

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- Close HTML tags - Reduce whitespace

Inline redundant package-private method that wraps

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Objects.requireNonNull()

Use Assertions.assertInstanceOf()

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hemanth0525 added 5 commits September 2, 2024 21:25

Add findDuplicates

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Merge branch 'feature/findDuplicates' of https://github.com/hemanth05…

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…25/commons-collections into feature/findDuplicates

Merge branch 'apache:master' into master

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Merge branch 'master' of https://github.com/apache/commons-collections …

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…into feature/findDuplicates

Add findDuplicates

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hemanth0525 added 4 commits September 3, 2024 23:21

Merge branch 'apache:master' into master

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Merge branch 'apache:master' into feature/findDuplicates

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Add diverse test cases for IterableUtils.duplicateList:

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- Mixed element types - Nested collections - Custom objects - Large-scale data - Immutable collections

Merge branch 'master' of https://github.com/hemanth0525/commons-colle…

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…ctions into feature/findDuplicates

Corrected spaces and lines

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hemanth0525 added 4 commits September 9, 2024 00:07

Merge branch 'apache:master' into feature/findDuplicates

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Add more Comprehensive tests IterableUtils.duplicateList

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- Mixed element types - Nested collections - Custom objects - Large-scale data - Immutable collections

Merge branch 'feature/findDuplicates' of https://github.com/hemanth05…

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…25/commons-collections into feature/findDuplicates

remove duplicate imports

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hemanth0525 closed this by deleting the head repository Sep 11, 2024

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Add findDuplicates Method to ListUtils with Comprehensive Test Cases #537

Add findDuplicates Method to ListUtils with Comprehensive Test Cases #537

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Add findDuplicates Method to ListUtils with Comprehensive Test Cases #537

Add findDuplicates Method to ListUtils with Comprehensive Test Cases #537

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hemanth0525 commented Aug 31, 2024

Summary

Why This Change?

How This Change is Useful

Example Usage

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