Add variables in documentation.

README.md

@@ -2,7 +2,7 @@ java
 =========
 
 <img src="https://docs.ansible.com/ansible-tower/3.2.4/html_ja/installandreference/_static/images/logo_invert.png" width="10%" height="10%" alt="Ansible logo" align="right"/>
-<a href="https://travis-ci.org/robertdebock/ansible-role-java"> <img src="https://travis-ci.org/robertdebock/ansible-role-java.svg?branch=master" alt="Build status"/></a> <img src="https://img.shields.io/ansible/role/d/22732"/> <img src="https://img.shields.io/ansible/quality/22732"/>
+<a href="https://travis-ci.org/robertdebock/ansible-role-java"> <img src="https://travis-ci.org/robertdebock/ansible-role-java.svg?branch=master" alt="Build status"/></a> <img src="https://img.shields.io/ansible/role/d/"/> <img src="https://img.shields.io/ansible/quality/"/>
 
 Install and configure java on your system.
 
@@ -35,6 +35,45 @@ The machine you are running this on, may need to be prepared.
 
 Also see a [full explanation and example](https://robertdebock.nl/how-to-use-these-roles.html) on how to use these roles.
 
+Role Variables
+--------------
+
+These variables are set in `defaults/main.yml`:
+```yaml
+---
+# defaults file for java
+
+# Set the vendor of java, valid values are "openjdk" and "oracle".
+java_vendor: openjdk
+
+# Set the variable to install the type, valid values are "jre" and "jdk".
+java_type: jre
+
+# Set the version of java, valid values are "6", 7", "8", "9", "10", "11",
+# "12" or "13".
+# By default, a distibution default is used, mapped in `vars/main.yml`.
+# By setting java_version, you overwrite this default to your selected
+# version.
+# java_version: 8
+
+# Set the format of the installation source, valid values are "targz" and
+# "rpm". This is only valid with "java_vendor == oracle"
+java_format: targz
+
+# Where do the RPMs come from when installing Oracle RPMs?
+# Either "local" or "repository".
+# Valid for "java_vendor == oracle" and "java_format" == "rpm"
+java_rpm_source: local
+
+# Choose if you can JCE installed. Only applicable for (both):
+# - java_vendor == "oracle"
+# - java_version == "8"
+java_jce: yes
+
+# In case of "java_vendor == oracle" and "java_format == targz", a directory
+# as to be set where to install.
+java_install_directory: /opt
+```
 
 Requirements
 ------------