javaseminor

7/27/2019 JavaSeminor

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TOKGISL

WELCOME


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JAVA


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What is JAVA?

A high level Programming Language.

Java was developed by a group of people at Sun

Microsystems, Inc. in 1991.

Original need for the language.

Redefined need.

Difference with the Native language C .


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Why JAVA?4

Object Oriented

Simple & Secure

Architecture Neutral

Portable & Robust Interpreted

High Performance

Distributed Dynamic

Multi-threaded

AWT & Event Handling

Write Once;Run Anywhere,any time,forever


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Heart of JAVA


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Installing JAVA

Download the Java Development Kit (JDK) for yourplatform. (Its free)

Run the .exe file to install java on your machine.(or)

Follow the instructions given.


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Setting Path

Start Control Panel System Advanced

Click on Environment Variables, under SystemVariables, find PATH, and click on it.

In the Edit windows, modifyPATH by adding the

location of the class to the value for PATH. If you do nothave the item PATH, you may select to add a newvariable and add PATH as the name and the location ofthe class as the value.

Close the window. (Or)

In command prompt

set classpath=%path%;.; (Or)

set path=location of class;


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Compilation & Execution

To Compile

javac xxx.java

To Execute

java xxx


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Elements

Identifiers: names the programmer chooses Keywords: names already in the programming language

Separators (also known as punctuators): punctuationcharacters and paired-delimiters

Operators: symbols that operate on arguments and produceresults

Literals(specified by their type) Numeric: int,float and double

Logical:boolean

Textual: char and String Reference: null

Comments

Line//

Block/* */


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Data Types

There are two data types available in Java:

Primitive Data Types

Reference/Object Data Types


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Operator

An operator is a symbol (+,-,*,/) that

directs the computer to performcertain mathematical or

logical manipulations

and is usually used to manipulate

data and variables


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Control Statements

Selection Statements if, if-else, if-else-if ladder, nested if-else

switch-case

Iteration Statements while do-while

for

Nested loops

Jump Statements break

continue

return


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First JAVA Program

public class First

{

public static void main(String args[])

{System.out.println(Java is my passion);

}

}


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What all are Object?

KGiSL - iTech

Tangible Things as a car, printer, ...

Roles as employee, boss, ...

Incidents as flight, overflow, ... Interactions as contract, sale, ...

Specifications as colour, shape,


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What is Object?

An object is like ablack box.

The internaldetails arehidden.

an object represents anindividual, identifiable item,unit, or entity, either real orabstract, with a well-definedrole in the problem domain.

Or

An "object" is anything towhich a concept applies.

Etc.


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Classes

The general form of a class definition is shown here:

class ClassName {

type instance-variable1;

// ...

type instance-variableN;

type methodName1(parameter-list) {

// body of method

}

// ...

type methodNameN(parameter-list) {

// body of method

}

}


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Elements of Classes

The data, or variables, defined within a class are calledinstancevariables.

The code is contained within methods.

Collectively, the methods and variables defined within a class arecalled members of the class.

Example:

class Vehicle {

int passengers; // number of passengers

int fuelcap; // fuel capacity in gallons

int mpg; // fuel consumption in miles per gallon// Display the range.

void range() {

System.out.println("Range is " + fuelcap * mpg);

}


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Creating Objects

Vehicle minivan; /* declare reference toobject */

minivan = new Vehicle(); /* allocate aVehicle object */

(or)

Vehicle minivan = new Vehicle(); /*create a Vehicle object called minivan*/

minivan.fuelcap= 16; /* Accessing themember of the Vehicle class */


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Example

class Vehicle {int passengers; // number of passengers

int fuelcap; // fuel capacity in gallons

int mpg; // fuel consumption in miles per gallon

Vehicle(int p, int f, int m) {

passengers = p;

fuelcap = f;

mpg = m;

}

// Display the range.void range() {

System.out.println("Range is " + fuelcap * mpg);

}

}


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class AddMeth {

public static void main(String args[]) {

Vehicle minivan = new Vehicle();Vehicle sportscar = new Vehicle(2,14,12);

// assign values to fields in minivan

minivan.passengers = 7;

minivan.fuelcap = 16;

minivan.mpg = 21;

System.out.print("Minivan can carry " +

minivan.passengers +". ");

minivan.range(); // display range of minivan

System.out.print("Sportscar can carry " +sportscar.passengers +". ");

sportscar.range(); // display range of sportscar.

}

}


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static keyword

class StaticDemo {int x; // a normal instance variable

static int y; // a static variable

}

class SDemo {


StaticDemo ob1 = new StaticDemo();

StaticDemo ob2 = new StaticDemo();

ob1.x = 10;

ob2.x = 20;

System.out.println("Of course, ob1.x and ob2.x "+

"are independent.");

System.out.println("ob1.x: " + ob1.x +

"\nob2.x: " + ob2.x);


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/* Each object shares one copy of

a static variable. */

System.out.println("The static variable y isshared.");

ob1.y = 19;

System.out.println("ob1.y: " + ob1.y + "\nob2.y:" + ob2.y);

System.out.println("The static variable y can be"+ " accessed through its class.");

StaticDemo.y = 11; /* Can refer to y throughclass name */

System.out.println("StaticDemo.y: " +StaticDemo.y + "\nob1.y: " + ob1.y + "\nob2.y: "+ ob2.y);

}

}


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Array Variables

Declaration type var-name[ ];//E.g: int arr[ ];

Memory Allocation

array-var = newtype[size]; // arr=new int[5]; Types: Single and Multi-Dimensional Array

Jagged Array- Different column sized array

Alternative Array Declaration int a[ ] = new int[5];

int[ ] a = new int[5];


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Using Command Line Arguments

A command-line argument is the information that directlyfollows the programs name on the command line when it isexecuted.

They are stored as strings in the String arraypassed to

main( ). Example:

class CommandLine {


for(int i=0; i


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Inheritance

Using inheritance, you can create a general classthat defines traits common to a set of relateditems.

This class can then be inherited by other, morespecific classes, each adding those things that areunique to it.

A class that is inherited is called a superclass.

The class thatdoes the inheriting is called asubclass.


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Types of Inheritance

Single Inheritance Multi Level Inheritance

Hierarchal Inheritance Multiple Inheritance

Hybrid Inheritance

A

B

A

B

C

A

B C

D E

A B

C

A

B C

D E

F


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Polymorphism

Overloading In Java it is possible to define two or more methods within the

same class that share the same name, as long as their returntype and parameter declarations(signature) are different.

Overriding In a class hierarchy, when a method in a subclass has the

same name and type signature as a method in its

superclass, then the method in the subclass is said to overridethe method in the superclass.


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Abstract class31

Anyclass that contains one or more abstract methodsmust also be declared abstract.

To declare a class abstract, you simply use the abstractkeyword in front of the class keyword at thebeginning of

the class declaration.

An abstract class cannot be directlyinstantiated, but canbe inherited.

Any subclass of an abstract class must either implementall of the abstractmethods in the superclass, or be itselfdeclared abstract.


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String Class

Stringis probably the most commonly usedclass in Javas class library.

Every string that created is actually an object of

type String. Even string constants are actuallyString

objects.String myString = "this is a test";

Java defines one operator for String objects: +.String myString = "I" + " like " + "Java.";


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Packages

Packagesare containers for classes that are used to keep theclass name space compartmentalized.

The package is both a naming and a visibility controlmechanism.

You can define classes inside a package that are not accessible bycode outside that package.

You can also define class members that are only exposed to othermembers of the same package.

This is the general form of the package statement:package pkg;


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Visibility Level34

PrivateNo

ModifierProtected Public

Same class Yes Yes Yes Yes

Same packagesubclass

No Yes Yes Yes

Same package

non-subclass

No Yes Yes Yes

Different package

subclass

No No Yes Yes

Different package

non-subclass

No No No Yes

Note: A class has only two possible access levels default and public.


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Interfaces

Defines what a class must do but not how it will do it. Using the keyword interface, you can fully abstract a

class interface from its implementation.

Once it is defined, any number of classes can implementan interface.

Also, one class can implement any number of interfaces.

one interface,multiple methods


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Java I/O

Java does provide strong, flexible support for I/O as itrelates to files and networks.

Javas I/O system is cohesive and consistent.

Java programs perform I/O through streams.

Astreamis an abstraction that either produces orconsumes information.

Input stream can abstract many different kinds of input:from a disk file, a keyboard, or a network socket.

Output stream may refer to the console, a disk file, or anetwork connection.

Java implements streams within class hierarchies definedin thejava.io package.


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Types of Streams

Java 2 defines two types of streams

Byte StreamsCharacter Streams

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Character Streams

Characterstreamsprovide a convenient means forhandling input and output of characters.

Character streams are defined by using two classhierarchies.

At the top are two abstract classes,ReaderandWriter.

The abstract classes Reader andWriter define severalkey methods that the other stream classes implement.

Two of the most important methods are read( )andwrite( ).

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The Predefined Streams

System Class

Stream Variables in, out, err

System.outrefers to the standard output stream.

System.inrefers to standard input stream.

System.errrefers to the standard error stream.

System.in is an object of type InputStream;System.out and System.err are objects of typePrintStream.

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C l I t U i Ch t


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Console Input Using CharacterStreams

The best class for reading console input isBufferedReader, which supports a buffered input stream.

Use InputStreamReader, which converts bytes tocharacters.

To obtain an InputStreamReaderobject, use the constructorshown here:

InputStreamReader(InputStreaminputStream)

Since System.inrefers to an object of type InputStream,it can be used for inputStream.

To construct a BufferedReaderuse the constructor shownhere:

BufferedReader(Reader inputReader)

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Exception Handling

An exception is an error that occurs at run time.

Exception handling subsystem streamlines error

handling by allowing your program to define a blockof code, called an exception handler, that isexecuted automatically when an error occurs.

Another reason that exception handling is importantis that Java defines standard exceptions for commonprogram errors.


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Fundamentals

try: Program statements that you want to monitor for exceptions are

contained within a tryblock.

catch: If an exception occurs within the try block, it is thrown. Your code can

catch this exception (using catch) and handle it in some rational

manner. throw:

System-generated exceptions are automatically thrown by the Javarun-time system. To manuallythrow an exception, use the keywordthrow.

throws:

Any exception that is thrown out of a method must be specified assuch by a throwsclause.

finally:Any code that absolutelymust be executed upon exiting from a try

block is put in a finallyblock.


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Example

// Demonstrate exception handling.class ExcDemo {

public static void main(String args[]) {int nums[] = new int[4];try {System.out.println("Before exception is

generated.");// Generate an index out-of-bounds exception.

nums[7] = 10;System.out.println("won't displayed");

}catch(ArrayIndexOutOfBoundsException exc){// catch the exceptionSystem.out.println(Array out of range!");

}System.out.println("After catch statement.");

}

}


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Uncaught Exception

// Let JVM handle the error.class NotHandled {


int nums[] = new int[4];

System.out.println("Before exception.");

//generate an index out-of-bounds exception

nums[7] = 10;

}

}

OUTPUT:

Before exception.

Exception in thread "main"

java.lang.ArrayIndexOutOfBoundsException: 7

at NotHandled.main(NotHandled.java:9)


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Thread Model

Threads exist in several states.

A thread can be running.

It can be ready to run as soon as it gets CPU time.

A running thread can be suspended.

A suspended thread can then be resumed.

A thread can be blockedwhen waiting for aresource.

At any time, a thread can be terminated.


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The main Thread

When a Java program starts up, main threadwhich is created automatically, begins runningimmediately.

It is the thread from which other child threads willbe spawned.

It must be the last thread to finish execution.

It can be controlled through a Threadobject. To get the reference were having the following

method

static Thread currentThread( )

E l


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// Controlling the main Thread.

class CurrentThreadDemo {

public static void main(String args[]) {Thread t = Thread.currentThread();

//Prints thread name, priority, name of the group

System.out.println("Current thread: " + t);

t.setName("My Thread"); //change the thread name

System.out.println("After name change: " + t);try {

for(int n = 5; n > 0; n--) {

System.out.println(n);

Thread.sleep(1000); //suspends thread

}

}

catch (InterruptedException e) {

System.out.println("Main thread interrupted");

}

}

}

Example


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Type Wrappers

Primitive types, rather than objects, are used for these quantitiesfor the sake of performance.

The primitive types are not part of the object hierarchy, and theydo not inherit Object.

Java provides type wrappers, which are classes thatencapsulate a primitive type within an object.

The type wrappers are Double, Float, Long, Integer, Short,Byte, Character, and Boolean, which are packaged in

java.lang.

All of the numeric type wrappers inherit the abstract classNumber.

Number declares methods that return the value of an object ineach of the different numeric types.


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Float Float(double num)

Float(float num)

Float(String str) throws NumberFormatException

Double Double(double num)

Double(String str) throws NumberFormatException

Constants:MIN_VALUE - Minimum value

MAX_VALUE - Maximum value


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Converting Numbers to/from Strings

Following methods will convert String object tonumeric types.parseByte()

parseShort()

parseInt()

parseLong()...

Following methods will convert numeric values to

String object. toString()

toBinaryString()

toHexString()

toOctalString()...


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Character Wrapper

The constructor for Character is Character(char ch)

Some methods in this class are

static boolean isDigit(char ch) static boolean isLetter(char ch)

static boolean isLetterOrDigit(char ch)

static boolean isLowerCase(char ch)

static boolean isUpperCase(char ch) static boolean isWhitespace(char ch)

static char toLowerCase(char ch)

static char toUpperCase(char ch)

static char toTitleCase(char ch)


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Boolean Wrapper

Boolean is a very thin wrapper

It contains the constants TRUE and FALSE

Boolean defines these constructors:Boolean(boolean boolValue)

Boolean(String boolString)

This class has some methods liketoString(), equals(),booleanValue() andvalueOf()


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Database Connectivity

Steps :

1) Loading the Driver into application

2) Getting the connection

3) Getting the Permission

4) Executing Sql statements


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EVENT HANDLING


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NETWORKING


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J2EE


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N-Tier J2EE Architecture

Web Tier EJB Tier

l f hi


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J2EE Platform Architecture

B2BApplications

B2C

Applications

Web

Services

WirelessApplications

Application Server EnterpriseInformation

Systems

ExistingApplications

l


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Servlet

Its a Java program. Handle the request from the client and send the

response.

Its a thread based program. Types:

Generic Servlet Protocol Independent

HTTP Servlet Protocol Dependent

Servlet API: javax.servlet.*;

javax.servlet.http.*;


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S i M


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Session Management

Maintaining the clients state.

Types:1. Hidden Form Fields

2. URL Rewriting

3. Cookies4. Session


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RMI


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EJB


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