A presentation discussing Java Beans, Exception Handling, Generics, Namespaces, and the Java Collections.

1. 1
Java Advanced
Features
Trenton Computer Festival
March 17, 2018
Michael P. Redlich
@mpredli
about.me/mpredli/

2. Who’s Mike?
• BS in CS from
• “Petrochemical Research Organization”
• Java Queue News Editor, InfoQ
• Ai-Logix, Inc. (now AudioCodes)
• Amateur Computer Group of New Jersey
2

3. Objectives (1)
• Java Beans
• Exception Handling
• Generics
• Java Database Connectivity
• Java Collections Framework
3

4. Java Beans
4

5. What are Java Beans?
• A method for developing reusable Java
components
• Also known as POJOs (Plain Old Java Objects)
• Easily store and retrieve information
5

6. Java Beans (1)
• A Java class is considered a bean when it:
• implements interface Serializable
• defines a default constructor
• defines properly named getter/setter methods
6

7. Java Beans (2)
• Getter/Setter methods:
• return (get) and assign (set) a bean’s data
members
• Specified naming convention:
•getMember
•setMember
•isValid
7

8. 8
// PersonBean class (partial listing)
public class PersonBean implements Serializable {
private static final long serialVersionUID = 7526472295622776147L;
private String lastName;
private String firstName;
private boolean valid;
public PersonBean() {
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
// getter/setter for firstName
public boolean isValid() {
return valid;
}
}

9. Demo Time…
9

10. Exception Handling
10

11. What is Exception
Handling?
• A more robust method for handling errors
than fastidiously checking for error codes
• error code checking is tedious and can obscure
program logic
11

12. Exception Handling (1)
• Throw Expression:
• raises the exception
• Try Block:
• contains a throw expression or a method that
throws an exception
12

13. Exception Handling (2)
• Catch Clause(s):
• handles the exception
• defined immediately after the try block
• Finally Clause:
• always gets called regardless of where exception
is caught
• sets something back to its original state
13

14. Java Exception Model
(1)
• Checked Exceptions
• enforced by the compiler
• Unchecked Exceptions
• recommended, but not enforced by the compiler
14

15. Java Exception Model
(2)
• Exception Specification
• specify what type of exception(s) a method will
throw
• Termination vs. Resumption semantics
15

16. 16
// ExceptionDemo class
public class ExceptionDemo {
public static void main(String[] args) {
try {
initialize();
}
catch(Exception exception) {
exception.printStackTrace();
}
public void initialize() throws Exception {
// contains code that may throw an exception of type Exception
}
}

17. Demo Time…
17

18. Generics
18

19. What are Generics?
• A mechanism to ensure type safety in Java
collections
• introduced in Java 5
• Similar concept to C++ Template
mechanism
19

20. Generics (1)
• Prototype:
• visibilityModifier class |
interface name<Type> {}
20

21. 21
// Iterator demo *without* Generics...
List list = new ArrayList();
for(int i = 0;i < 10;++i) {
list.add(new Integer(i));
}
Iterator iterator = list.iterator();
while(iterator.hasNext()) {
System.out.println(“i = ” + (Integer)iterator.next());
}

22. 22
// Iterator demo *with* Generics...
List<Integer> list = new ArrayList<Integer>();
for(int i = 0;i < 10;++i) {
list.add(new Integer(i));
}
Iterator<Integer> iterator = list.iterator();
while(iterator.hasNext()) {
System.out.println(“i = ” + iterator.next());
}

23. 23
// Defining Simple Generics
public interface List<E> {
add(E x);
}
public interface Iterator<E> {
E next();
boolean hasNext();
}

24. Java Database
Connectivity (JDBC)
24

25. What is JDBC?
• A built-in API to access data sources
• relational databases
• spreadsheets
• flat files
• The JDK includes a JDBC-ODBC bridge for
use with ODBC data sources
• type 1 driver
25

26. Java Database
Connectivity (1)
• Install database driver and/or ODBC driver
• Establish a connection to the database:
• Class.forName(driverName);
• Connection connection =
DriverManager.getConnection();
26

27. Java Database
Connectivity (2)
• Create JDBC statement:
•Statement statement =
connection.createStatement();
• Obtain result set:
• Result result =
statement.execute();
• Result result =
statement.executeQuery();
27

28. 28
// JDBC example
import java.sql.*;
public class DatabaseDemo {
public static void main(String[] args) {
String sql = “SELECT * FROM timeZones”;
Class.forName(“sun.jdbc.odbc.JdbcOdbcDriver”);
Connection connection =
DriverManager.getConnection(“jdbc:odbc:timezones”,””,””);
Statement statement = connection.createStatement();
ResultSet result = statement.executeQuery(sql);
while(result.next()) {
System.out.println(result.getDouble(2) + “ “
+ result.getDouble(3));
}
connection.close();
}
}

29. Java Collections
Framework
29

30. What are Java
Collections? (1)
• A single object that groups together
multiple elements
• Collections are used to:
• store
• retrieve
• manipulate
30

31. What is the Java
Collection Framework?
• A unified architecture for collections
• All collection frameworks contain:
• interfaces
• implementations
• algorithms
• Inspired by the C++ Standard Template
Library
31

32. What is a Collection?
• A single object that groups together
multiple elements
• sometimes referred to as a container
• Containers before Java 2 were a
disappointment:
• only four containers
• no built-in algorithms
32

33. Collections (1)
• Implement the Collection interface
• Built-in implementations:
• List
• Set
33

34. Collections (2)
• Lists
• ordered sequences that support direct
indexing and bi-directional traversal
• Sets
• an unordered receptacle for elements
that conform to the notion of
mathematical set
34

35. 35
// the Collection interface
public interface Collection<E> extends Iterable<E>{
boolean add(E e);
boolean addAll(Collection<? extends E> collection);
void clear();
boolean contains(Object object);
boolean containsAll(Collection<?> collection);
boolean equals(Object object);
int hashCode();
boolean isEmpty();
Iterator<E> iterator();
boolean remove(Object object);
boolean removeAll(Collection<?> collection);
boolean retainAll(Collection<?> collection);
int size();
Object[] toArray();
<T> T[] toArray(T[] array);
}

36. Iterators
• Used to access elements within an ordered
sequence
• All collections support iterators
• Traversal depends on the collection
• All iterators are fail-fast
• if the collection is changed by something other
than the iterator, the iterator becomes invalid
36

37. 37
// Iterator demo
import java.util.*;
List<Integer> list = new ArrayList<Integer>();
for(int i = 0;i < 9;++i) {
list.add(new Integer(i));
}
Iterator iterator = list.iterator();
while(iterator.hasNext()) {
System.out.println(iterator.next());
}
0 1 2 3 4 5 6 7 8
current last

38. Demo Time…
38

39. Java IDEs (1)
• IntelliJ IDEA 2017.3
•jetbrains.com/idea
• stay tuned for version 2018.1 coming soon
• Eclipse IDE
•eclipse.org/ide
39

40. Java IDEs (2)
• NetBeans 8.2
•netbeans.org
• currently being moved from Oracle to Apache
40

41. Local Java User Groups
(1)
• ACGNJ Java Users Group
• facilitated by Mike Redlich
• javasig.org
• Princeton Java Users Group
• facilitated byYakov Fain
• meetup.com/NJFlex
41

42. Local Java User Groups
(2)
• NYJavaSIG
• facilitated by Frank Greco
• javasig.com
• PhillyJUG
• facilitated by Martin Snyder, et. al.
• meetup.com/PhillyJUG
42

43. Local Java User Groups
(3)
• Capital District Java Developers Network
• facilitated by Dan Patsey
•cdjdn.com
• currently restructuring
43

44. Further Reading
44

45. Upcoming Events
• ACGNJ Java Users Group
• Dr. Venkat Subramaniam
• Monday, March 19, 2018
• DorothyYoung Center for the Arts, Room 106
• Drew University
• 7:30-9:00pm
• “Twelve Ways to Make Code Suck Less”
45

46. 46
Thanks!
mike@redlich.net
@mpredli
redlich.net
slideshare.net/mpredli01
github.com/mpredli01

47. Upcoming Events
• March 17-18, 2017
•tcf-nj.org
• April 18-19, 2017
•phillyemergingtech.com
47