This document provides resources and information about Java programming topics relevant to the Oracle Certified Java Programmer Level 2 exam, including class design principles, generics, collections, exceptions, I/O, threads, localization, inheritance vs interfaces vs abstract classes, object composition, design patterns like singleton, DAO, and abstract factory. Links are provided to external pages with more detailed explanations and code examples for each topic.

1. ORACLE CERTIFIED JAVA PROGRAMMER - LEVEL 2
Sayed Ahmed
Computer Engineering, BUET, Bangladesh
Masters from the University of Manitoba, Canada
http://www.justetc.net
http://sayed.justetc.net
sayed@justetc.net

2. TOPICS
Java Class Design
Advanced Class Design
Object-Oriented Design Principles
Generics and Collections
String Processing
Exceptions and Assertions
Java I/O Fundamentals
Java File I/O (NIO.2)
Building Database Applications with JDBC
Threads
Concurrency
Localization

3. TOPICS IN DETAIL
 http://www.javainmind.com/exam2-
table/exam2-checklist/

4. INHERITANCE VS INTERFACE VS ABSTRACT CLASS
 http://stackoverflow.com/questions/5816563/when-should-i-
choose-inheritance-over-an-interface-when-designing-c-sharp-
class
 Their general recommendations are as follows:
 Do favor defining classes over interfaces.
 Do use abstract classes instead of interfaces to decouple the
contract from implementations. Abstract classes, if defined correctly,
allow for the same degree of decoupling between contract and
implementation.
 Do define an interface if you need to provide a polymorphic hierarchy
of value types.
 Consider defining interfaces to achieve a similar effect to that of
multiple inheritance.
 Chris Anderson expresses particular agreement with this last tenant, arguing
that:
 Abstract types do version much better, and allow for future extensibility, but they also
burn your one and only base type. Interfaces are appropriate when you are really
defining a contract between two objects that is invariant over time. Abstract base types
are better for defining a common base for a family of types.

5. INHERITANCE VS INTERFACE VS ABSTRACT CLASS
 http://stackoverflow.com/questions/3311788/when-to-implement-an-
interface-and-when-to-extend-a-superclass
 Use an interface if you want to define a contract. I.e. X must take Y
and return Z. It doesn't care how the code is doing that. A class can
implement multiple interfaces.
 Use an abstract class if you want to define default behaviour in non-
abstract methods so that the endusers can reuse it without rewriting it
again and again. A class can extend from only one other class. An
abstract class with only abstract methods can be as good definied as an
interface. An abstract class without any abstract method is
recognizeable as the Template Method pattern (see this answer for
some real world examples).
 An abstract class in turn can perfectly implement an interface whenever
you want to provide the enduser freedom in defining the default
behaviour.

6. JAVA INTERFACES
 http://docs.oracle.com/javase/tutorial/java/Ian
dI/createinterface.html

7. DEVELOP CODE THAT IMPLEMENTS "IS-A" AND/OR "HAS-A" RELATIONSHIPS
 http://www.javacamp.org/moreclasses/oop/o
op5.html
 http://www.primeinspiration.com/more/progra
mming/programming-guides/892-is-a-and-
has-a-relationships.html

8. OBJECT COMPOSITION
 http://stackoverflow.com/questions/3979581/
disadvantage-of-object-composition-over-
class-inheritance
 http://en.wikipedia.org/wiki/Composition_over
_inheritance

9. OOP DESIGN PRINCIPLES
 http://userpages.umbc.edu/~tarr/dp/lectures/
OOPrinciples.pdf

10. DESIGN A CLASS USING THE SINGLETON DESIGN
PATTERN.
 http://www.javaworld.com/javaworld/jw-04-
2003/jw-0425-designpatterns.html?page=2
 http://en.wikipedia.org/wiki/Singleton_pattern
 http://en.wikipedia.org/wiki/Singleton_pattern
 http://www.vogella.com/articles/DesignPatter
nSingleton/article.html

11. WRITE CODE TO IMPLEMENT THE DAO PATTERN
 http://www.oracle.com/technetwork/java/dataacc
essobject-138824.html
 Use a Data Access Object (DAO) to abstract and
encapsulate all access to the data source. The
DAO manages the connection with the data
source to obtain and store data.
 http://java.boot.by/ocpjp7-upgrade/ch02s03.html
 http://www.oracle.com/technetwork/java/dataacc
essobject-138824.html
 http://www.oracle.com/technetwork/java/dataacc
essobject-138824.html

12. ABSTRACT FACTORY METHOD
 http://stackoverflow.com/questions/5739611/diff
erences-between-abstract-factory-pattern-and-
factory-method
 The main difference between a "factory method" and
an "abstract factory" is that the factory method is a
single method, and an abstract factory is an object
 there is an object A, who wants to make a Foo
object. Instead of making the Foo object itself (e.g.
with a factory method), it's going get a different
object (the abstract factory) to create the Foo object.
 http://en.wikipedia.org/wiki/Abstract_factory_patt
ern