cronn commons-lang

Add the following Maven dependency to your project:

<dependency>
    <groupId>de.cronn</groupId>
    <artifactId>commons-lang</artifactId>
    <version>1.5</version>
</dependency>

This library includes the following classes, which are described in detail in the sections below:

• StreamUtil: Collectors and utilities that are useful when working with Java streams
• Action: An interface that is similar to Runnable but allows to throw checked exceptions
• AlphanumericComparator: A comparator that implements the Alphanum Algorithm which is useful to sort versions or filenames in a more

StreamUtil

toSingleElement()

Good case:

Object number = Stream.of(1, 2, 3)
    .filter(value -> value > 2)
    .collect(StreamUtil.toSingleElement());
// number = 3

Bad case:

Object number = Stream.of(1, 2, 3, 4)
    .filter(value -> value > 2)
    .collect(StreamUtil.toSingleElement());
// Throws IllegalStateException: Exactly one element expected but got 2: [3, 4]

toSingleOptionalElement()

Similar to toSingleElement() but returns an Optional and throws no exception if no element was found.

Optional<Object> number = Stream.of(1, 2, 3)
    .filter(value -> value > 2)
    .collect(StreamUtil.toSingleOptionalElement());

toLinkedHashSet()

StreamUtil.toLinkedHashSet() is a drop-replacement for Collectors.toSet() that guarantees a stable/deterministic order.

Example:

// numbers contains 1, 2, 3 and returns the elements in exactly this order when iterating
SequencedSet<Object> numbers = Stream.of(1, 2, 3, 2, 3)
    .collect(StreamUtil.toLinkedHashSet());

SetUtils

SetUtils provides utility methods for creating ordered sets in Java.

Unlike Set.of(…), SetUtils.orderedSet(…) maintains the order of elements as they are added.

Example Usage

SequencedSet<String> ordered = SetUtils.orderedSet("abc", "def", "ghi");
// Output: [abc, def, ghi]

SequencedSet<Integer> numbers = SetUtils.orderedSet(3, 1, 2, 1);
// Output: [3, 1, 2]

Key Difference: SetUtils.orderedSet(…) uses LinkedHashSet, ensuring insertion order is preserved.

AlphanumericComparator

People sort strings with numbers differently than software does. Most sorting algorithms compare ASCII values, which produces an ordering that is inconsistent with human logic.

Consider the following list of filenames:

file1.txt
file2.txt
file10.txt
file3.txt

If you sort this list using the default sort order, the result will be:

file1.txt
file10.txt
file2.txt
file3.txt

This order is not intuitive for most people.

However, by using the AlphanumericComparator, you will get:

file1.txt
file2.txt
file3.txt
file10.txt

This order is more natural and aligns with human expectations.

Requirements

• Java 21+