Java Advanced Features
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The document discusses advanced features of Java, including Java Beans, exception handling, generics, Java Database Connectivity (JDBC), and the Java Collections Framework. It provides definitions, examples, and code snippets to illustrate these concepts, showing how they enhance Java's functionality and programming efficiency. Additionally, the document highlights local Java user groups and upcoming events for further learning and community engagement.
![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
}
}](https://image.slidesharecdn.com/javaadvancedfeatures-180318142941/85/Java-Advanced-Features-16-320.jpg)
![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();
}
}](https://image.slidesharecdn.com/javaadvancedfeatures-180318142941/85/Java-Advanced-Features-28-320.jpg)
![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);
}](https://image.slidesharecdn.com/javaadvancedfeatures-180318142941/85/Java-Advanced-Features-35-320.jpg)
Java Advanced Features
- 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
- 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(); }
- 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(); } }
- 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
- 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
- 47. Upcoming Events • March 17-18, 2017 •tcf-nj.org • April 18-19, 2017 •phillyemergingtech.com 47