Painless has a strict whitelist for methods and classes to ensure all
painless scripts are secure. Most of these methods are exposed directly
from the Java Runtime Environment (JRE) while others are part of
Elasticsearch or Painless itself. Below is a list of all available
classes grouped with their respected methods. Clicking on the method
name takes you to the documentation for that specific method. Methods
defined in the JRE also have a (java 9) link which can be used to see
the method’s documentation in Java 9.