In Java, static final variables are constants and the convention is that they should be in upper-case. However, I have seen that most people declare loggers in lower-case which comes up as a violation in PMD.
e.g:
private static final Logger logger = Logger.getLogger(MyClass.class);
Just search googleor SO for "static final logger" and you will see this for yourself.
Should we be using LOGGER instead?
The logger reference is not a constant, but a final reference, and should NOT be in uppercase. A constant VALUE should be in uppercase.
private static final Logger logger = Logger.getLogger(MyClass.class);
private static final double MY_CONSTANT = 0.0;