The API says that it can return any element, but in practice it returns
the first element. I've never seen it return any other element.
`list.parallelStream().findAny()` doesn't do a lot better. Some short
testing shows that although it doesn't return the first element, it
still always returns the same element.
On 25/08/2025 17:22, Chen Liang wrote:
Hi Daniel, can you explain why `list.stream().findAny()` does not fulfill your
needs? This also returns a random element and is also very concise.
-Chen Liang
________________________________
From: core-libs-dev <core-libs-dev-r...@openjdk.org> on behalf of Daniel Tavares
<cet...@gmail.com>
Sent: Saturday, August 23, 2025 2:36 PM
To: core-libs-dev@openjdk.org <core-libs-dev@openjdk.org>
Subject: Proposal: Add getRandom() default method to java.util.List
Dear OpenJDK community,
I’d like to propose the addition of a getRandom() default method to the
java.util.List interface.
As a Java developer with over 15 years of experience, I’ve often found myself
needing to retrieve a random element from a list. While this can be achieved
using ThreadLocalRandom or by shuffling the list, these approaches require
boilerplate code and are not immediately intuitive—especially for newcomers to
the language.
Motivation
Retrieving a random element from a list is a common task in many domains:
* Games and simulations
* Educational tools
* Random sampling in data processing
* Lightweight testing scenarios
Adding a default method like getRandom() would improve readability and reduce
friction for developers, particularly those learning Java or working on rapid
prototyping.
Proposed Method
default T getRandom() {
if (isEmpty()) return null;
int index = ThreadLocalRandom.current().nextInt(size());
return get(index);
}
Alternatively, the method could throw NoSuchElementException if the list is
empty, depending on what the community considers more idiomatic.
Benefits
* Improved developer experience: Simplifies a common use case.
* Better readability: Expresses intent directly.
* Minimal impact: Can be added as a default method without breaking
existing implementations.
* Alignment with modern Java: Leverages default methods introduced in Java
8.
I understand that additions to core interfaces are considered carefully, and I
welcome feedback on whether this idea aligns with the design philosophy of the
Java Collections Framework.
Thank you for your time and consideration.
Best regards,
Daniel Perin Tavares
Curitiba, Brazil
