是否有Java构建方式可以将2个整数组合成一个Set？

Question

This is my code:

private class UniqueClassByTwoIntProperties {
    private final int propertyOne;
    private final int propertyTwo;

    UniqueCase(final int propertyOne, final int propertyTwo) {
        this.propertyOne= propertyOne;
        this.propertyTwo= propertyTwo;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }

        if (this == obj) {
            return true;
        }

        if (!(obj instanceof UniqueCase)) {
            return false;
        }

        UniqueClassByTwoIntProperties unique = (UniqueClassByTwoIntProperties) obj;

        return unique.claimApplicationId == claimApplicationId && unique.claimCoverageId == claimCoverageId;
    }

    @Override
    public int hashCode() {
        return Objects.hash(propertyOne, propertyTwo);
    }
}

I am looping through a list with objects, where I want to get the unique's in the following way:

myList.stream()
      .map(row -> new UniqueClassByTwoIntProperties(row.getOne(), row.getTwo()))
      .collect(Collectors.toSet());

I was wondering if there was a build-in class/method in Java. I have looked into dictionaries and MultiMapValues, but it was a bit hacky.

Answer 1

You can simply do it as:

Set<UniqueClassByTwoIntProperties> uniques = new HashSet<>(myList);

Aside : Make sure the hashCode and equals of the objects are implemented correctly for the object to be comparable.

If you just want the List of uniques then you can use Stream.distinct as :

List<UniqueClassByTwoIntProperties> uniques = myList.stream()
                                 .distinct() // for unique objects
                                 .collect(Collectors.toList());