java tutorial for beginners learning.ppt

1-1
Introduction to Java Programming

1-2
Focus of the Course
• Object-Oriented Software Development
 problem solving
 program design, implementation, and testing
 object-oriented concepts
• classes
• objects
• encapsulation
• inheritance
• polymorphism

Introduction
1-3
The Java Programming Language
Program Development
Object-Oriented Programming

Introduction
• One characteristic that is constant in the software
industry today is the “CHANGE”.
• Change is one of the most critical aspects of
Software Development and Management.
• Since the invention of the Computer, many
programming approaches have been tried. Such
as modular programming, top-down programming,
bottom-up programming and structured
programming.
© 2004 Pearson Addison-Wesley. All rights reserved 1-4

1-5
JAVA
• A programming language specifies the words and
symbols that we can use to write a program
• A programming language employs a set of rules
that dictate how the words and symbols can be put
together to form valid program statements
• The Java programming language was created by
Sun Microsystems, Inc.
• It was introduced in 1995 and it's popularity has
grown quickly since

JAVA
• Like C, C++ etc. Java is another computer
language but with a difference.
• Java’s designers have borrowed the best features
of many existing language such as C and C++ and
added a few new features to form a simple
language.
• One of the important reason for java’s success is
the amazing functionality it adds to the WWW.

• Java has two lives, one as a stand-alone computer
language for general purpose programming and
the other as a supporting language for Internet
programming.
• The general purpose programs are known as
applications and the programs written for internet
are known as applets.

1-8
Java Program Structure
• In the Java programming language:
 A program is made up of one or more classes
 A class contains one or more methods
 A method contains program statements
• These terms will be explored in detail throughout
the course
• A Java application always contains a method
called main

1-9
Hello.java
class abc
{
public static void main (String[] args)
{
System.out.println (“hello world");
}
}

1-10
public class MyProgram
{
}
// comments about the class
class header
class body
Comments can be placed almost anywhere

1-11
public class MyProgram
{
}
// comments about the class
{
}
// comments about the method
method header
method body

• Public:- The keyword ‘public’ is a access
specifier that declares the main method
as unprotected and therefore making it
accessible to all other classes.
• Static:- Next appears the keyword ‘static’, which
declares this method as one that belongs
to the entire class and not a part of any
object of class. The main must always be
declared as static since the interpreter
uses this method before any objects are
created.

• Void:- This type modifier ‘void’ states that the
main method does not return any values.
• All parameters to a method are declared inside a
pair of parentheses. Here, String args [ ] declares a
parameter named args, which contains an array of
objects of the class type String.

Lets see what happens at runtime:-

1-15
Comments
• Comments in a program are called inline
documentation
• They should be included to explain the purpose
of the program and describe processing steps
• They do not affect how a program works
• Java comments can take three forms:
// this comment runs to the end of the line
/* this comment runs to the terminating
symbol, even across line breaks */
/** this is a javadoc comment */

1-16
Identifiers
• Identifiers are the words a programmer uses in a
program
• An identifier can be made up of letters, digits, the
underscore character ( _ ), and the dollar sign
• Identifiers cannot begin with a digit
• Java is case sensitive - Total, total, and
TOTAL are different identifiers
• By convention, programmers use different case
styles for different types of identifiers, such as
 title case for class names - hello
 upper case for constants - MAXIMUM

1-17
Reserved Words
• The Java reserved words:
abstract
assert
boolean
break
byte
case
catch
char
class
const
continue
default
do
double
else
enum
extends
false
final
finally
float
for
goto
if
implements
import
instanceof
int
interface
long
native
new
null
package
private
protected
public
return
short
static
strictfp
super
switch
synchronized
this
throw
throws
transient
true
try
void
volatile
while

1-18
Outline
Program Development

1-19
Program Development
• The mechanics of developing a program include
several activities
 writing the program in a specific programming language
(such as Java)
 translating the program into a form that the computer can
execute
 investigating and fixing various types of errors that can
occur
• Software tools can be used to help with all parts of
this process

1-20
Programming Languages
• Each type of CPU executes only a particular
machine language
• A program must be translated into machine
language before it can be executed
• A compiler is a software tool which translates
source code into a specific target language
• Often, that target language is the machine
language for a particular CPU type
• The Java approach is somewhat different

1-21
Java Translation
• The Java compiler translates Java source code
into a special representation called bytecode
• Java bytecode is not the machine language for any
traditional CPU
• Another software tool, called an interpreter,
translates bytecode into machine language and
executes it
• Therefore the Java compiler is not tied to any
particular machine
• Java is considered to be architecture-neutral

1-22
Java Translation
Java source
code
Machine
code
Java
bytecode
Bytecode
interpreter
Bytecode
compiler
Java
compiler

1-23
Development Environments
• There are many programs that support the
development of Java software, including:
 Sun Java Development Kit (JDK)
 Sun NetBeans
 IBM Eclipse
 Borland JBuilder
 MetroWerks CodeWarrior
 BlueJ
 jGRASP
• Though the details of these environments differ,
the basic compilation and execution process is
essentially the same

1-24
Syntax and Semantics
• The syntax rules of a language define how we can
put together symbols, reserved words, and
identifiers to make a valid program
• The semantics of a program statement define what
that statement means (its purpose or role in a
program)
• A program that is syntactically correct is not
necessarily logically (semantically) correct
• A program will always do what we tell it to do, not
what we meant to tell it to do

1-25
Errors
• A program can have three types of errors
• The compiler will find syntax errors and other
basic problems (compile-time errors)
 If compile-time errors exist, an executable version of the
program is not created
• A problem can occur during program execution,
such as trying to divide by zero, which causes a
program to terminate abnormally (run-time errors)
• A program may run, but produce incorrect results,
perhaps using an incorrect formula (logical errors)

1-26
Basic Program Development
errors
errors
Edit and
save program
Compile program
Execute program and
evaluate results

1-27
Outline
Program Development

1-28
Problem Solving
• The purpose of writing a program is to solve a
problem
• Solving a problem consists of multiple activities:
 Understand the problem
 Design a solution
 Consider alternatives and refine the solution
 Implement the solution
 Test the solution
• These activities are not purely linear – they
overlap and interact

1-29
Problem Solving
• The key to designing a solution is breaking it down
into manageable pieces
• When writing software, we design separate pieces
that are responsible for certain parts of the
solution
• An object-oriented approach lends itself to this
kind of solution decomposition
• We will dissect our solutions into pieces called
objects and classes

1-30
• Java is an object-oriented programming language
• As the term implies, an object is a fundamental
entity in a Java program
• Objects can be used effectively to represent real-
world entities
• For instance, an object might represent a
particular employee in a company
• Each employee object handles the processing and
data management related to that employee

1-31
Objects
• An object has:
 state - descriptive characteristics
 behaviors - what it can do (or what can be done to it)
• The state of a bank account includes its account
number and its current balance
• The behaviors associated with a bank account
include the ability to make deposits and
withdrawals
• Note that the behavior of an object might change
its state

1-32
Classes
• An object is defined by a class
• A class is the blueprint of an object
• The class uses methods to define the behaviors of
the object
• The class that contains the main method of a Java
program represents the entire program
• A class represents a concept, and an object
represents the embodiment of that concept
• Multiple objects can be created from the same
class

1-33
Data and Expressions
Character Strings
Variables and Assignment
Primitive Data Types
Expressions
OOP

1-34
Character Strings
• A string of characters can be represented as a
string literal by putting double quotes around the
text:
• Examples:
"This is a string literal."
"123 Main Street"
"X"
• Every character string is an object in Java, defined
by the String class
• Every string literal represents a String object

1-35
The println Method
• In the hello program studied earlier, we invoked
the println method to print a character string
• The System.out object represents a destination
(the monitor screen) to which we can send output
System.out.println (“hello world");
object method
name
information provided to the method
(parameters)

1-36
The print Method
• The System.out object provides another service
as well
• The print method is similar to the println
method, except that it does not advance to the
next line
• Therefore anything printed after a print statement
will appear on the same line

1-37
Countdown.java
public class Countdown
{
//-----------------------------------------------------------------
// Prints two lines of output representing a rocket countdown.
//-----------------------------------------------------------------
{
System.out.print ("Three... ");
System.out.print ("Two... ");
System.out.print ("One... ");
System.out.print ("Zero... ");
System.out.println ("Liftoff!"); // appears on first output line
System.out.println ("Houston, we have a problem.");
}
}

1-38
String Concatenation
• The string concatenation operator (+) is used to
append one string to the end of another
"Peanut butter " + "and jelly"
• It can also be used to append a number to a string
• A string literal cannot be broken across two lines
in a program

1-39
Facts.java
public class Facts
{
{
// Strings can be concatenated into one long string
System.out.println ("We present the following facts for your "
+ "extracurricular edification:");
System.out.println ();
// A string can contain numeric digits
System.out.println ("Letters in the Hawaiian alphabet: 12");
// A numeric value can be concatenated to a string
System.out.println ("Dialing code for Antarctica: " + 672);
System.out.println ("Year in which Leonardo da Vinci invented "
+ "the parachute: " + 1515);
System.out.println ("Speed of ketchup: " + 40 + " km per year");
}
}

1-40
String Concatenation
• The + operator is also used for arithmetic addition
• The function that it performs depends on the type
of the information on which it operates
• If both operands are strings, or if one is a string
and one is a number, it performs string
concatenation
• If both operands are numeric, it adds them
• The + operator is evaluated left to right, but
parentheses can be used to force the order

1-41
Addition.java
public class Addition
{
//-----------------------------------------------------------------
// Concatenates and adds two numbers and prints the results.
//-----------------------------------------------------------------
{
System.out.println ("24 and 45 concatenated: " + 24 + 45);
System.out.println ("24 and 45 added: " + (24 + 45));
}
}

1-42
Escape Sequences
• What if we wanted to print a the quote character?
• The following line would confuse the compiler
because it would interpret the second quote as the
end of the string
System.out.println ("I said "Hello" to you.");
• An escape sequence is a series of characters that
represents a special character
• An escape sequence begins with a backslash
character ()
System.out.println ("I said "Hello" to you.");

1-43
Escape Sequences
• Some Java escape sequences:
Escape Sequence
b
t
n
r
"
'

Meaning
backspace
tab
newline
carriage return
double quote
single quote
backslash

1-44
Roses.java
public class Roses
{
//-----------------------------------------------------------------
// Prints a poem (of sorts) on multiple lines.
//-----------------------------------------------------------------
{
System.out.println ("Roses are red,ntViolets are blue,n" +
"Sugar is sweet,ntBut I have "commitment issues",nt"
+
"So I'd rather just be friendsntAt this point in our " +
"relationship.");
}
}

1-45
Variables
• A variable is a name for a location in memory
• A variable must be declared by specifying the
variable's name and the type of information that it
will hold
int total;
int count, temp, result;
Multiple variables can be created in one declaration
data type variable name

1-46
Variable Initialization
• A variable can be given an initial value in the
declaration
• When a variable is referenced in a program, its
current value is used
int sum = 0;
int base = 32, max = 149;

1-47
PianoKeys.java
public class PianoKeys
{
//-----------------------------------------------------------------
// Prints the number of keys on a piano.
//-----------------------------------------------------------------
{
int keys = 88;
System.out.println ("A piano has " + keys + " keys.");
}
}

1-48
Assignment
• An assignment statement changes the value of a
variable
• The assignment operator is the = sign
total = 55;
• The value that was in total is overwritten
• You can only assign a value to a variable that is
consistent with the variable's declared type
• The expression on the right is evaluated and the
result is stored in the variable on the left

1-49
Geometry.java
public class Geometry
{
{
int sides = 7; // declaration with initialization
System.out.println ("A heptagon has " + sides + " sides.");
sides = 10; // assignment statement
System.out.println ("A decagon has " + sides + " sides.");
sides = 12;
System.out.println ("A dodecagon has " + sides + " sides.");
}
}

1-50
Constants
• A constant is an identifier that is similar to a
variable except that it holds the same value during
its entire existence
• As the name implies, it is constant, not variable
• The compiler will issue an error if you try to
change the value of a constant
• In Java, we use the final modifier to declare a
constant
final int MIN_HEIGHT = 69;

Constants
• Constants are useful for three important reasons
• First, they give meaning to otherwise unclear
literal values
 For example, MAX_LOAD means more than the literal 250
• Second, they facilitate program maintenance
 If a constant is used in multiple places, its value need
only be updated in one place
• Third, they formally establish that a value should
not change, avoiding inadvertent errors by other
programmers

Oop
Java is an object oriented programming language.
Its main concepts are:-
1. Inheritance
2. Polymorphism
3. Exception handling

1. Inheritance
• Reusability is aspect of OOP paradigm. It is always
nice if we could reuse something that already exist
rather than creating the same all over again. Java
support this concept. This is basically done by
creating new classes, reusing the properties
existing on.
• Inheritance can be defined as the process where
one object acquires the properties of another. With
the use of inheritance the information is made
manageable in a hierarchical order.

Types
• Single Inheritance
• Multilevel Inheritance
• Hierarchical Inheritance
• Multiple Inheritance

Extends & Implements
• When we talk about inheritance, the most
commonly used keyword would be extends and
implements. These words would determine
whether one object IS-A type of another. By using
these keywords we can make one object acquire
the properties of another object.
• We inherit class from existing class throw
‘extends’ keyword but java does not directly
extends more than one class. However this
concept is implements using secondary
inheritance path in the form of ‘interface’ using
implements keyword.

Extends
Let us see how the extends keyword is used to
achieve inheritance.
Class vehicle
{
…………..
}
class car extends vehicle
{
…………..
}

Implements
Interface color
{
………….
}
Class Car implements color
{
…………..
}

Example:-
Class vehicle
{
String vehiceType;
}
interface Colour
{
String car_colour;
}

Public class car extends vehicle implements colour
{
String modelType;
Public void showdetail()
{
vehicaltype=“car”;
modeltype=“sports”;
car_colour=“red”;
System.out.println(modelType+vehicleType+car_colour);
}

public static void main(String[] args)
{
Car car=new car();
Car.showdetail();
}
}

Output:-
Sports car red

2.Polymorphism:-
• Polymorphism is the ability of an object to take on
many forms. The most common use of polymorphism
in OOP occurs when a parent class reference is used
to refer to a child class object.
• Any Java object that can pass more than one IS-A test
is considered to be polymorphic. In Java, all Java
objects are polymorphic since any object will pass the
IS-A test for their own type and for the class Object.

Example:-
Class game
{
Public void type()
{
System.out.println(“Indoor & outdoor”);
}
}
Class cricket extends game
{
Public void type()
{
System.out.println(“outdoor game”)}

Public static void main(String[] args)
{
Game gm= new Game();
Cricket ck= new cricket();
gm.type();
ck.type();
gm=ck;
gm.type();
}
}

Output:-
Indoor & outdoor
Outdoor game
Outdoor game

3. Exception handling:-
• An exception is a problem that arises during the
execution of a program. An exception can occur for
many different reasons, including the following:-
=> A user has entered invalid data.
=> A file that needs to be opened cannot be found.
=> A network connection has been lost in the middle of
communications or the JVM has run out of memory.

To understand how exception handling works in Java,
you need to understand the three categories of
exceptions:
• Checked exceptions: A checked exception is an
exception that is typically a user error or a problem
that cannot be foreseen by the programmer. For
example, if a file is to be opened, but the file cannot be
found, an exception occurs. These exceptions cannot
simply be ignored at the time of compilation.
• Runtime exceptions: A runtime exception is an
exception that occurs that probably could have been
avoided by the programmer. As opposed to checked
exceptions, runtime exceptions are ignored at the time
of compilation.

• Errors: These are not exceptions at all, but problems
that arise beyond the control of the user or the
programmer. Errors are typically ignored in your code
because you can rarely do anything about an error.
For example, if a stack overflow occurs, an error will
arise. They are also ignored at the time of compilation.

Exception Hierarchy:-
The exception class is a subclass of the Throwable
class. Other than the exception class there is another
subclass called Error which is derived from the
Throwable class.

Note:- some exceptions cant be handeld, they leads
to unexpected program termination. These type of
exceptions are called Uncaught exceptions.
For example:-
Class uncaught exception
{
Public static void main(String[] args)
{
Int a=0;
Int b=7/a;
}
}

Output:-

java tutorial for beginners learning.ppt

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