File BankAccount.java describes BankAccount objects (instances of class BankAccount)
BankAccount.java has two audiences
people (programmers like us)
the Java compiler
Java files always start with comments
a convention good programs honor
not a rule in the Java language, but a rule for us
Comments are for people to read: Java doesnt care
//
text up to end of line is a comment
/**
special javadoc comment more later */
/*
old style comment rare */