QUESTIONS WITH SOLUTIONS GRADED A+
◉ Class. Answer: Blueprint/prototype from which objects are created
◉ Inheritance. Answer: subclasses can inherit states/behaviors of
superclasses
◉ interface. Answer: contract between class and outside world; when a
class implements an interface, it promises to provide the behavior
published by that interface
◉ package. Answer: a namespace for organizing classes & interfaces in
a logical manner; makes large software projects easier to manage
◉ Encapsulation. Answer: Hiding the internal state of an object and
requiring all interaction to be performed through an object's methods
(accessors and mutators).
Example: In a Bicycle class, method changeGear() could be
implemented so as to only accept values between 1 and 6
,◉ Benefits of Objects. Answer: Modularity
Information-Hiding
Code re-use
Pluggability and debugging ease
◉ Modularity. Answer: source code for an object can be
written/maintained independently of source code for other objects.
objects can be easily passed around the system once they've been
created.
◉ Information-Hiding. Answer: By interacting only with object's
methods, details of internal implementation stay secret from outside
world.
◉ Code re-use. Answer: Complex objects only need to be coded once;
you can use classes that have already been created by others.
◉ Pluggability/Debugging Ease. Answer: If an object is causing
problems, you can easily remove it and put something else in its place.
Example: replace a bolt that is broken, not the whole machine.
◉ How to use the changeGear() method on a Bicycle bike1?. Answer:
bike1.changeGear();
,◉ How many superclasses can a subclass have?. Answer: ONLY ONE
◉ How many subclasses can inherit from the same superclass?. Answer:
Infinitely many
◉ What is the main benefit of using inheritance?. Answer: The subclass
contains all of the methods/fields of the superclass, but the subclass'
code focuses on the unique aspects, making code simpler and easier to
read.
◉ Why must the superclass' code be carefully documented?. Answer:
Because that code is not physically in the subclass.
◉ Interface. Answer: the methods that a class is required to contain;
empty methods that are related
◉ Should the methods in an interface be public or private?. Answer:
MUST be public
◉ Packages. Answer: organizes a set of related classes/interfaces; like a
folder on your computer
◉ class library. Answer: a set of packages
, ◉ API. Answer: Application Programming Language: Java's library of
classes that you can use in your own applications.
◉ What do the Java API's packages represent? Give examples.. Answer:
tasks for general purpose programming: String, File, Socket, some for
developing GUIs.
◉ What is a benefit of using packages?. Answer: It allows developers to
focus on the design of an application and NOT the technical stuff that
makes it work.
◉ Real-world objects contain BLANK and BLANK.. Answer: State,
behavior
◉ A software object's state is stored in BLANK. Answer: fields
◉ A software object's behavior is exposed through BLANK. Answer:
methods (functions)
◉ Hiding internal data from the outside world, and accessing it only
through publicly exposed methods is known as data BLANK. Answer:
Encapsulation