The document discusses the final keyword in Java and its applications to classes, methods, and variables. When applied to a class, final means the class cannot be sub-classed, and when applied to a method it means the method cannot be overridden in a subclass. For variables, final means the variable can only be initialized once and must be assigned a value either at declaration or in every constructor for non-static variables and static initializers for static variables to avoid compile-time errors.

1. Java final Keyword
Sujit Kumar
Zenolocity LLC
Copyright @ 2012

2. final applied to Class and Methods
• When applied to a class it means the class
cannot be sub-classed.
• When applied to a method, it means that the
method cannot be overridden in a subclass.

3. final applied to a variable
• A final variable can only be initialized once, either via
an initializer or an assignment statement.
• It does not need to be initialized at the point of
declaration: this is called a "blank final" variable.
• A blank final instance variable of a class must be
definitely assigned at the end of every constructor of
the class in which it is declared
• Similarly, a blank final static variable must be definitely
assigned in a static initializer of the class in which it is
declared
• Otherwise, a compile-time error occurs in both cases.