This does not work for me. Java image that takes 30 seconds to build on x86 machine took 40 minutes to build on M1 after which I killed it. So this feature essentially does not exist as it's not usable. I don't think that's how most people use it. I, personally, rent x86 VPS just for docker.
Most images nowadays have ARM version, so probably that's how most people use it.
Yes, we need a compiler for Java. Java sources are compiled to Java bytecode along with many other actions for complex projects like downloading dependencies, generating sources, running tests which might run platform-dependent binaries and so on.
> That was the advantage given for the JVM. The .jar ran on x86 and ARM.
Yes, wasm and Java bytecode are the same in that regard. But Java bytecode failed to get adoption outside of Java world. Wasm might not, we will see. One significant improvement of Wasm over Java is good security story. Java sandbox is well known for its CVEs. Browser wasm implementations are battle-tested on billions of devices in the wild Internet. So you basically can't run untrusted Java bytecode without further boundaries like KVM or at least containers. But you definitely can run untrusted Wasm bytecode because that's what your browser does all the time.
Most images nowadays have ARM version, so probably that's how most people use it.