Exploring Collectors by Venkat Subramaniam

One of the most intriguing classes in the JDK is the Collectors utility class, with a collection of some highly powerful functions that are useful during the reduce operation of streams.

The functions that are in this class have so much to offer and yet, due to their complex nature, often are not used as much as they should be. Using well defined live coded examples, we will take up several common programming problems.

Discuss them quickly and drive the implementation of these using the Collectors methods. By the end of this presentation you will know more throughly the power of Collectors and how to apply the methods in there.

He has trained and mentored thousands of software developers in the US, Canada, Europe, and Asia, and is a regularly-invited speaker at several international conferences. Venkat helps his clients effectively apply and succeed with sustainable agile practices on their software projects.

[RahulKumar-gpbg]

I don’t know why I haven’t watched this video before. Thanks @Venkat sir. You are a gem.

[CostaKazistov]

Venkat is phenomenal teacher. Of all Java speakers on YouTube, he is my favourite. I've been watching his talks since about 2015. In many ways his style of teaching is even better than most online courses.

[sankarpandiarajan]

Saw a comment in another of Venkat's talks..."the best stand-up comedian". he absolutely is...amazing how effortlessly he walks over such complex stuff.
the mutant jaws...creating a new species with "mapFlattening" vs "flatMap" - man!!! hilarious.

[skootdiggity]

Oracle should add an honorary Yeeinteger class for Venkat.

[ruixue]

51:42 motivation of groupingBy
51:56 imperative way of grouping - 52:11 question to resolve
57:00 groupingBy

[anversadhat]

"Haskel feels like Cathedral and Java is like Bazzar" :) 17:00
"It works" 21:45

[monsterhuntergo]

I'm now a fan... I just started following him and a nice way to update my skills too. Functional programming is in-line with clean coding as well. Thanks so much for sharing.. Hope to have more of your videos.. Hope there are also updated videos of him.. :)

[ricardotrejoruiz]

The golden conference everybody need to watch.

[ErfanHossainShoaib]

One word for you, "Eloquent". Thank you Sir.

[techpatil]

My favorite guy, best thing i learn from him👌

[nguyenquan]

Very fun when he talk about flat map. Thank sir

[mangeshpawar]

Excellent explanation of stream collectors

[truth-]

Here is how to get the oldest Person in every City: (value = Optional)

Map<String, Optional<Person>> oldestPersonByCity =
.collect( groupingBy(Person::getCity,

[B-Billy]

58:35 CameraMan is also lazy like Java Streams :)

[amazingvipul]

mapFlatten to flatMap reasoning was hilarious :D

[peter.g]

One minor correction, the term "idempotent function" means something different - it means applying the function on a result it gives yields again the same result. Sorting is a good example - if you have a list and you sort it, it can change, but if you sort it again, it stays the same.

[dcngn_]

Man I learned to love streams, but I know how it felt like to see them when I haven't learned about them yet.. I wonder how my supervisor will feel like when he sees my thesis full of streams.

[mehmoodrehman]

1. Java and Functional Programming 0:00
a. Lazy evaluation vs eager evaluation
2. Common operations: filter 2:00, map 5:50, reduce 6:20

3. Functions should be pure
4. Avoid shared mutability
5. A little example
…gone wrong
6. The right way, - delegate, be declarative,
7. collect is a reduce operation
8. Collectors utility class
9. toList, toSet 30:00
10. Should we not honor immutability?
leave it to the APIs

[rydmerlin]

How is teeing() different from reducing()?

[truth-]

This is how get the name of the oldest Person with one statement:
No NEED for collect(), no need for maxBy(), no need for collectingAndThen().

String nameOfOldestPerson =

not found");

Sometimes Venkat exaggerate a little bit :-)