I can recommend the Raspberry Pi.

Also check out:-

Pi top

For cool wrappers around the core device.

Introduces Linux, comes with Scratch, Python and the means to get java, C, C++ etc

Also NOOBS software also includes Mathematica and Wolfram.


Getting started with Mathematica

Also, the latest Raspbian Jessie release appears to include BlueJ an integrated development environment (IDE) specifically designed to teach object-oriented programming in Java.

I found this out when my DD and I assembled her Pi-top last Friday. She is into Steven Universe and most identifies with Peridot so she loves the lurid green colour. The fact that she now can carry it around the house because it is a 'laptop' is a huge upgrade too.

She has been using a Pi for the past couple of years and the Pi 3 is definitely a step up because it comes with wifi and Bluetooth sparing USB ports that would otherwise be occupied by the dongles.

Also, because Raspbian is a Linux variant it comes with gcc/g++ which can be used to compile C/C++ from the command line interface (CLI).