- are made ONLY from these Unicode characters:

letters(upper/lowercase)

digits(0-9)

the underscore(_)

currency symbols($, €, £, ₤ etc.)

- MUST NOT START with a digit

- are case-sensitive(Volatile != volatile)

- there is NO limit to how long they ca be

- MUST NOT be a: boolean literal(true, false), Null literal(null),

nor any of Java's 50 keywords(abstract, assert, boolean, break, byte, case, catch, char, class, const, continue, default, do, double, else, enum, extends, final, finally, float, for, goto, if, implements, import, instanceof, int, interface, long, native, new, package, private, protected, public, return, ..., volatile, while)

_____________________________________

=> "#", ".", "-", ":", "null", "true" and "continue" will NOT compile.

line 16 - the question is asking about valid Java(not JavaBeans) indentifiers