A field variable is a variable that is declared as a member of a class. A local variable is a variable that is declared local to a method.
this() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.
A final class cannot be inherited. A final method cannot be overridden in a subclass. A final field cannot be changed after it's initialized, and it must include an initializer statement where it's declared.
An abstract class cannot be instantiated. Abstract methods may only be included in abstract classes. However, an abstract class is not required to have any abstract methods, though most of them do. Each subclass of an abstract class must override the abstract methods of its superclasses or it also should be declared abstract.
Transient variable is a variable that may not be serialized.