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Comment by cornstalks | Hacker News Reader

How do people deal with old clients? The Android app I (partially) work on can't even use JDK 8 (I learned this when trying to use Double.hash() to hash a double).

Coming from C++, where I can use C++20 and still deploy to ancient devices, I'm seriously baffled how people work with Java. Is there any way to use new JDK features in an Android app that also has to deploy to Android SDK 21 (i.e. Android 5.0 from 2014!)?

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Android doesn’t use proper Java, it runs their own bastard child of it. You can sometimes get away with byte code desugaring of more modern features sometimes, and it has been getting better recently, but it is far from ideal.

If you develop for Android you likely use either Kotlin or Flutter; either way there's very little in this Java release that matters or should excite you. Kotlin has already had most of the features that Java has been adding over the last few releases in some form or another and most Android users use those a lot. So, from that point of view there are maybe a few things that Kotlin could do nicer but nothing world shocking.

The things I'm most interested in are JNI-related. Project Panama[1] will bring a ton of improvements. These aren't stable in JDK 21 but I'm anticipating their stability in the near(ish) future (JDK 22? 23?). I'd like to experiment with some of the preview APIs in JDK 21 but given I can't even use JDK 8 I'm wondering if I'm just SOL and if I should abandon all hope for me using things from Project Panama.

[1]: https://openjdk.org/projects/panama/

Most Android development is done in Kotlin which is where Java has been copying it's features from for the last 5 years. In that way, Android programming has been the future of Java programming today. But now Java has basically caught up, I blame this on Kotlin having lost focus on multiplatform and having stopped innovating new language features.

Cross-compilation is possible. (See javac -target.)

I'm not sure what the current matrix of support for this is.

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