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Comment by Marqin | Hacker News Reader

Also worth noting is that most of SIM cards are Java cards, running Java applets

Java Card is not very similar to Java, Javascript is more like Java than Java Card is

To my understanding it’s an actual subset of Java, a very limited subset, but a subset of the real Java nonetheless. Java Card applets are compiled using a real Java compiler, and then the bytecode is translated into a simplified format for running on the card.

This video from defcon gives a good overview of what Java Card applets is, the limitations and what it can do: https://www.youtube.com/watch?v=31D94QOo2gY

It doesn't resemble JS. It's a JVM/Java subset. You can even write apps using the Java Servlet API with JC 3.x

That's only on JavaCard 3 connected, though – which is dead: https://stackoverflow.com/questions/9546812/javacard-3-in-re...

But I agree – Java to JavaScript is not the best comparison. Maybe a better one would be C programs written for a Unix system vs. C on a microcontroller: Same language; vastly different instruction set, OS and hardware capabilities and APIs available.

Unlike C on microcontrollers, Java Card applications are hardware and OS agnostic, though!

That's what I said, it's so limited compared to Java that saying SIM cards run "a thing like Java" is massively overstating it. It doesn't even have floats.

It's a UICC not a SIM card anyway.

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