Ah, with Java applets presumably? Before my time… RIP Java Applets, 1990s – 2016 (or at least Oracle is deprecating them starting with the release of Java 9), hardly knew ye.
Interestingly, many ARM processors include Java support (such as the ARM926EJ-S, with “Jazelle® technology” on ARM9). Oracle developed several editions of Java: J2EE (enterprise), J2SE (standard), and… J2ME (micro edition). Supposedly J2ME is available for Android. But J2ME last I checked is quite limited, stuck on the 1.3 class file format (47, current modded Minecraft uses around Java 1.7 (51), plus or minus), porting it would be no trivial effort, but not to say it isn’t impossible. Another challenge is porting the graphics library from OpenGL to OpenGL ES / lwjgl. ES is much more limited.
Although, the WebGL 1.0 API which I am using in voxel-clientmc is actually based on OpenGL ES 2.0 (and there is an upcoming WebGL 2.0 based on OpenGL ES 3.0, but it is not yet widely supported), so it should be possible in principle.
If someone does succeed in modding MCPC to run on J2ME / OpenGL ES, I’ll give them mad props for the significant technical feat, but personally I’m more interested in developing on the web platform for the reasons mentioned above (or using web technologies in a desktop app using something like electron, but I haven’t looked into that yet). Another benefit is voxel-clientmc is completely open source, so in theory it should be easier to enhance and extend and do whatever you want with than modifying the official Minecraft client, but of course the downside is it is much buggier and feature-incomplete at the moment.