Java Advanced Features (TCF 2014)

1
Java Advanced
Features
Trenton Computer Festival
March 15, 2014
Michael P. Redlich
@mpredli
about.me/mpredli/
Sunday, March 16, 14

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

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

Java Beans
4

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

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

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

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;
}
}

Exception Handling
9

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
10

Exception Handling (1)
• Throw Expression:
• raises the exception
• Try Block:
• contains a throw expression or a method that
throws an exception
11

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
12

Java Exception Model
(1)
• Checked Exceptions
• enforced by the compiler
• Unchecked Exceptions
• recommended, but not enforced by the
compiler
13

Java Exception Model
(2)
• Exception Speciﬁcation
• specify what type of exception(s) a method will
throw
• Termination vs. Resumption semantics
14

15
// 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
}
}

Generics
16

What are Generics?
• A mechanism to ensure type safety in Java
collections
• introduced in Java 5
• Similar concept to C++ Template
mechanism
17

Generics (1)
• Prototype:
• visibilityModifier class |
interface name<Type> {}
18

19
// 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());
}

20
// Iterator demo *with* Generics...
List<Integer> list = new ArrayList<Integer>();
for(int i = 0;i < 10;++i) {
}
Iterator<Integer> iterator = list.iterator();
System.out.println(“i = ” + iterator.next());
}

21
// Defining Simple Generics
public interface List<E> {
add(E x);
}
public interface Iterator<E> {
E next();
boolean hasNext();
}

Java Database
Connectivity (JDBC)
22

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
23

Java Database
Connectivity (1)
• Install database driver and/or ODBC driver
• Establish a connection to the database:
• Class.forName(driverName);
• Connection connection =
DriverManager.getConnection();
24

Java Database
Connectivity (2)
• Create JDBC statement:
•Statement statement =
connection.createStatement();
• Obtain result set:
• Result result =
statement.execute();
• Result result =
statement.executeQuery();
25

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// 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();
}
}

Java Collections
Framework
27

What are Java
Collections? (1)
• A single object that groups together
multiple elements
• Collections are used to:
• store
• retrieve
• manipulate
28

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
29

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
30

Collections (1)
• Implement the Collection interface
• Built-in implementations:
• List
• Set
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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
32

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// 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);
}

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
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// Iterator demo
import java.util.*;
List<Integer> list = new ArrayList<Integer>();
for(int i = 0;i < 9;++i) {
}
Iterator iterator = list.iterator();
System.out.println(iterator.next());
}
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Live Demo!
36

Java IDEs (1)
• IntelliJ
• jetbrains.com/idea
• Eclipse
• eclipse.org
37

Java IDEs (2)
• NetBeans
• netbeans.org
• JBuilder
• embarcadero.com/products/
jbuilder
38

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
39

Local Java User Groups
(2)
• NewYork Java SIG
• facilitated by Frank Greco
• javasig.com
• Capital District Java Developers Network
• facilitated by Dan Patsey
• cdjdn.com
40

Java Advanced Features (TCF 2014)

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