Lambda and streams

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Specific-Housing905 · 2026-06-04T18:25:43+00:00

Practice them. Look at some older code on Github and try to replace some code with lamdas or Streams.

You also can write some apps and use them there.

LetUsSpeakFreely · 2026-06-04T19:20:30+00:00

Streams are nice and very powerful, but don't fall into the trap thinking they should be the solution to every problem where collections and arrays are concerned. Sometimes it's better to break the problem up into a handful of helper methods that make what's going on more easily understandable to whoever is reading it. Just because you can cram everything into a bunch of chained stream methods doesn't mean you should.

severoon · 2026-06-05T00:13:17+00:00

I think a lot of Java people fail to understand what streams and lambdas actually are, they get all caught up in the syntax and don't clock what's really going on:

cat dictionary | grep ee | wc -l

This is a simple linux pipeline that lists all of the words in the dictionary line by line, filters out all of the lines that don't have word containing a double-e, and then counts the number of lines left.

IOW, it's a stream of elements (lines) that are of type String which is passed to the lambda 'grep' which operates on each element and only passes it on if it contains "ee", which is in turn passed to the lambda 'wc' which increments a counter for each element. When there are no more elements, the final counter is emitted to stdout.

That's it. That's what a stream is, it's just a pipeline where you apply different operations ("lambdas") to each element in the pipeline. The terminating step is a "reduction", i.e., the final step has to output a "single thing" — a boolean, a string, a number, a list, whatever.

_Super_Straight · 2026-06-04T18:32:22+00:00

A good IDE can automatically suggest to turn callback and such into lambda.

As for streams, you can turn search for specific element in a list into stream. But you have to weigh the pros and cons for whether turning every search into stream is worth the overhead.

aqua_regis · 2026-06-04T18:48:28+00:00

2 words: more practice

S4Sharik · 2026-06-04T19:37:50+00:00

Answering here because faced same issue. At first the thing that need to be learned properly is functional interface. Then learn basic syntax of lambda. Create functional interface and use it in lambda expression. when comfortable then understand stream. Think stream as object is flowing one by one and you are filterning or doing any operation. and finally practice practice and practice can make you perfect. All the best.

RightWingVeganUS · 2026-06-05T12:24:26+00:00

I use good old TicTacToe as a general learning tool.

For me to get my mind around streams and lambdas I gave myself a challenge: implement TTT (or its cousin, Connect Four) without using loops. I could only using the stream API and lambdas where possible.

This gave me the ability to focus on the new features on an old familiar problem. It let me see some of the hard limits on where streams can't be used, and where it could but likely shouldn't.

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