add java tutorial (#2491)

java/doc/installation.rst

@@ -0,0 +1,61 @@
+Install Ray for Java
+====================
+
+Ray works for Java 8 and above. Currently, we only support building Ray from source.
+
+Build from source
+-----------------
+
+Install dependencies
+^^^^^^^^^^^^^^^^^^^^
+
+First, make sure JDK 8 or above is installed on your machine. If not, you can download it from `here <http://www.oracle.com/technetwork/java/javase/downloads/index.html>`_.
+
+Then install the following dependencies.
+
+For Ubuntu users, run the following commands:
+::
+
+  sudo apt-get update
+  sudo apt-get install -y maven cmake pkg-config build-essential autoconf curl libtool unzip flex bison python # we install python here because python2 is required to build the webui
+
+  # If you are not using Anaconda, you need the following.
+  sudo apt-get install python-dev  # For Python 2.
+  sudo apt-get install python3-dev  # For Python 3.
+
+  # If you are on Ubuntu 14.04, you need the following.
+  pip install cmake
+
+  pip install cython
+
+For macOS users, run the following commands:
+::
+
+  brew update
+  brew install maven cmake pkg-config automake autoconf libtool openssl bison wget
+
+  pip install cython
+
+Build Ray
+^^^^^^^^^
+
+Then we can start building Ray with the following commands:
+::
+
+  git clone https://github.com/ray-project/ray.git
+  cd ray
+
+  # build native components
+  ./build.sh -l java
+
+  # build java API
+  cd java
+  mvn clean install -Dmaven.test.skip
+
+Run tests
+^^^^^^^^^
+::
+
+  # in `ray/java` directory
+  export RAY_CONFIG=ray.config.ini
+  mvn test