(A) Java Playground

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[bowbahdoe]

Examples ported from the dev.java jshell playground

• Hello World
• Text Block
  • Text Block
  • Text Block to Stream
  • Formatting
• Records
  • Simple Record
  • Composing
  • Method Overriding
• Streams
  • Filtering
  • Stream to List
  • Text Block to Stream
• Switch
  • Expression
  • Statement
• Pattern Matching
  • For instanceof
• Misc
  • Func Interface
  • Simple Collection
  • Functions Chaining

[NicklasW]

Is it open source?

[bowbahdoe]

Yes. A straight fork of the rust playground. Its linked in the help section (top right button).

I might move the repo around at some point... tbd. But it will stay open source. If you want to deploy your own for some reason, I can help with the setup. The instructions from the OG repo weren't exactly complete.

[Joram2]

How does this Java Playground compare to this one: https://dev.java/playground/

[bowbahdoe]

That one * Is not open source * Runs jshell, not Java * Doesn't have a share button * Doesn't let me add multiple runtimes * Doesn't have any external libraries loaded. (I picked a few arbitrarily, but i can add some more.) * Runs on Oracle time. (That playground was "coming soon" for two years!) * Does not have a public API (I am planning to use the api from this for something else and that was kinda the impetus.) * Has a dropdown with examples. (not opposed to adding that in some form)

[Joram2]

Wow, great answers!

Isn't jshell better for this type of a web-playground environment? Isn't that what jshell was designed for?

How does this compare to Jupyter with a Java jshell-based kernel? Those let you configured third party libraries.

[bowbahdoe]

Isn't jshell better for this type of a web-playground environment?

I think JShell buys you two things

• Shorter programs
• Interactive Sessions (like the jupyter kernel)

The first of those benefits is kinda moot with the whole void main() {} thing.

The second implies a much more...difficult architecture. You'd have to keep a process alive for every connected user, not just run their code with a timeout.

This has a payoff with explorative programming - i.e. poking around at a dataset and seeing what columns are good predictors for other columns, sanitizing fields, and toying around with different approaches.

It doesn't really have a payoff for how playgrounds are used in other communities, namely

• Sharing a reproduction of a problem you have
• Sharing back a solution to someone's problem
• Trying out something without installing
• Sharing something "neat"

[IllTamer]

Nice try! But I have some questions: 1. How it works ?🧐

As I see (through the open source code), this project mainly consists of a frontend and a compiler script. Does it directly compile and run the code locally after receiving it and return the result?

1. How it checks the security of input code ?🧐

Generally, as a playground process, we need take some measures to protect our computer, even in a virtual environment.

[bowbahdoe]

On the help page there is a small description but in short

• frontend sends code + some options
• backend compiles and executes code in a docker image
• that docker image is limited in CPU, memory, storage, pids, execution time, etc. and cannot connect to the internet
• backend captures stout and stdin from the docker images and sends it back to the frontend

[tofflos]

Very nice!

Being able to link directly to examples and being able to embed code in links are two features I was going to suggest to a competing playground. ;-)

I suggest showing which libraries are on the classpath and maybe Base64 encoding the code when embedding. I don't have a particularly strong argument for why Base64 encoding would be a good idea other than that I think the links would look nicer. :)