2. 2
History
• High level programming language
• Developed by a team leaded by James Gosling
on 1991 at SunMicrosystems
• Previously it was called as Oak, renamed to Java
on 1995
• Current owner of Java Language- Oracle
3. 3
Getting Started
The java Development Kit-JDK .
• In order to get started in java
programming, one needs to get a recent
copy of the java JDK. This can be obtained
for free by downloading it from the Oracle
official website, JDK download Windows
• Once you download and install this JDK
you are ready to get started.
4. 4
• Compiler:
A program that translates
program written in a high level
language into the equivalent machine
language
• Java Virtual machine: A S/W which
make java programs machine
independent
5. 5
Characteristics of Java
• Java Is Simple
• Java Is Object-Oriented
• Java Is Interpreted
• Java Is Secure
• Java Is Portable
6. 6
Eclipse IDE
• https://www.eclipse.org/downloads/
Step by step procedure to download
https://www.geeksforgeeks.org/techtips/how-to-dow
nload-and-install-eclipse-on-windows
Steps to follow to create project, package and class
in eclipse
https://www.geeksforgeeks.org/selenium-with-java-
tutorial/
7. 7
A Simple Java Program
public class HelloWorld {
public static void main(String[] args){
System.out.println(“Hello World!”);
}
}
8. 8
Java Program may contain
• Comments
• Package
• Reserved words
• Blocks
• Classes
• Methods
• The main method
10. 10
Identifiers
• Identifiers are the names of variables,
methods, classes, packages and
interfaces.
• It cannot start with a digit.
• An identifier cannot be a reserved
word (public, class, static, void,
method,…)
11. 11
Note
• Java is case sensitive.
• File name has to be the same as class name
in file.
12. 12
Identifiers EXAMPLE
public class Test
{
public static void
main(String[] args)
{
int a = 20;
}
}
In the above Java code, we have 5
identifiers as follows:
• Test: Class Name
• main: Method Name
• String: Predefined Class Name
• args: Variable Name
• a: Variable Name
13. 13
Variables
• Each variable must be declared before
it is used.
• The declaration allocates a location in
memory to hold values of this type.
14. 14
Variable Declarations
• The syntax of a variable declaration is
data-type variable-name;
• Example:
• Assign values:
int total;
long count, sum;
total = 0;
count = 20, sum=50;
unitPrice = 57.25;
double unitPrice;
15. 15
Variable Declarations, cont.
• Declaring and Initializing in One Step
int total=0;
Long count=20, sum=50;
double unitPrice = 57.25;
16. 16
Variable Declaration
Example
public class DeclarationExample {
public static void main (String[] args) {
int weeks = 14;
long numberOfStudents = 120;
double averageFinalGrade = 78.6;
char ch=‘a’;
System.out.println(weeks);
System.out.println(numberOfStudents);
System.out.println(averageFinalGrade);
System.out.println(ch);
}
}
18. 18
Integers
• There are four integer data types, They
differ by the amount of memory used
to store them.
Type Bits Value Range
byte 8 -127 … 128
short 16 -32768 … 32767
int 32 about 9 decimal digits
long 65 about 18 decimal digits
19. 19
Floating Point
• There are two floating point types.
Type Bits Range
(decimal digits)
Precision
(decimal digits)
float 32 38 7
double 64 308 15
20. 20
Characters
• A char value stores a single
character from the Unicode character
set.
• A character set is an ordered list of
characters and symbols.
• ‘A’, ‘B’, ‘C’, … , ‘a’, ‘b’, … ,‘0’, ‘1’, … , ‘$’, …
• The Unicode character set uses 16 bits
(2 bytes) per character.
21. 21
Boolean
• A boolean value represents a
true/false condition.
• The reserved words true and
false are the only valid values for a
boolean type.
• The boolean type uses one bit.
23. 23
Basic Arithmetic Operators
Operator Meaning Type Example
+ Addition Binary total = cost + tax;
- Subtraction Binary cost = total – tax;
* Multiplication Binary tax = cost * rate;
/ Division Binary salePrice = original / 2;
% Modulus Binary remainder = value % 5;
24. 24
Increment and Decrement
Operators
Operator Meaning Example Description
++ preincrement ++var
Increments var by 1 and
evaluates the new value
in var after the
increment.
++ postincrement var++
Evaluates the original
value in var and
increments var by 1.
– – predecrement --var
Decrements var by 1
and evaluates the new
value in var after the
decrement.
– – postdecrement var--
Evaluates the original
value in var and
decrements var by 1.
25. 25
Increment and Decrement
Operators, cont.
int i = 10;
int newNum = 10 * (i++); int newNum = 10 * i;
i = i + 1;
Same effect as
int i = 10;
int newNum = 10 * (++i); i = i + 1;
int newNum = 10 * i;
Same effect as
28. 28
if Statement
Boolean
Expression
true
Statement(s)
false
(radius >= 0)
true
area = radius * radius * PI;
System.out.println("The area for the circle of " +
"radius " + radius + " is " + area);
false
(A) (B)
if (booleanExpression)
{
statement(s);
}
if (radius >= 0)
{
area = radius * radius * PI;
System.out.println("The area"
“ for the circle of radius "
+ "radius is " + area);
}
30. 30
if...else Statement
Example
if (radius >= 0)
{
area = radius * radius * 3.14159;
System.out.println("The area for the “
+ “circle of radius " + radius +
" is " + area);
}
else
{
System.out.println("Negative input");
}
31. 31
Multiple Alternative
if Statements
if (score >= 90.0)
grade = 'A';
else
if (score >= 80.0)
grade = 'B';
else
if (score >= 70.0)
grade = 'C';
else
if (score >= 60.0)
grade = 'D';
else
grade = 'F';
Equivalent
if (score >= 90.0)
grade = 'A';
else if (score >= 80.0)
grade = 'B';
else if (score >= 70.0)
grade = 'C';
else if (score >= 60.0)
grade = 'D';
else
grade = 'F';
32. 32
switch Statements
switch (switch-expression)
{
case value1:
statement(s)1;
break;
case value2:
statement(s)2;
break;
…
case valueN:
statement(s)N;
break;
default:
statement(s)-for-default;
}
The value1, ..., and valueN
must have the same data
type as the value of the
switch-expression.
The switch statement in Java is a
control flow statement that allows a
program to execute different blocks
of code based on the value of a
variable
or expression
33. 33
while Loop
while (loop-continuation-
condition)
{
// loop-body;
Statement(s);
}
int count = 0;
while (count < 100)
{
System.out.println("
Welcome to Java!");
count++;
}
Loop
Continuation
Condition?
true
Statement(s)
(loop body)
false
(count < 100)?
true
System.out.println("Welcome to Java!");
count++;
false
(A) (B)
count = 0;
In Java, a while loop is a control flow statement that repeatedly executes a block of code as long as a
specified condition remains true.
35. 35
for Loops
for (initial-action;
loop-continuation-
condition; action-
after-each-iteration)
{
// loop body;
Statement(s);
}
int i;
for (i = 0; i < 100; i++)
{
System.out.println(
"Welcome to Java!");
}
Loop
Continuation
Condition?
true
Statement(s)
(loop body)
false
(A)
Action-After-Each-Iteration
Intial-Action
(i < 100)?
true
System.out.println(
"Welcome to Java");
false
(B)
i++
i = 0
In Java, the for loop is a control flow statement that allows you to repeatedly execute a block of code. It's
particularly useful
when you know in advance how many times you need to iterate.
37. 37
Methods
A method is a collection of statements
that are grouped together to perform
an operation.
public int max(int num1, int num2)
{
int result;
if (num1 > num2)
result = num1;
else
result = num2;
return result;
}
modifier return value type method name formal parameters
return value
method
body
method
header
parameter list
Define a method Invoke a method
int z = max(x, y);
actual parameters
(arguments)
38. 38
Methods
• Modifier is like public, private and protected.
• returnType is the data type of the value the
method returns.
• Some methods perform the desired
operations without returning a value.
• In this case, the returnType is the keyword
void.
39. 39
Methods
• Parameters are Variables which
defined in the method header.
• Method body contains a
collection of statements that
define what the method does.
40. 40
Benefits of Methods
• Write a method once and reuse it
anywhere.
• Information hiding: Hide the
implementation from the user.
• Reduce complexity.
41. 41
Calling a Method
• If the method returns a value
• int larger = max(3, 4);
• If the method returns void, a call to the
method must be a statement.
• System.out.println("Welcome to Java!");
44. 44
public class TestMethodOverloading {
/** Main method */
public static void main(String[] args) {
// Invoke the max method with int parameters
System.out.println("The maximum between 3 and 4 is "+ max(3, 4));
// Invoke the max method with the double parameters
System.out.println("The maximum between 3.0 and 5.4 is"+ max(3.0,5.4));
}
/** Return the max between two int values */
public static int max(int num1, int num2) {
if (num1 > num2)
return num1;
else
return num2;
}
/** Find the max between two double values */
public static double max(double num1, double num2) {
if (num1 > num2)
return num1;
else
return num2;
}
}
45. 45
Scope of Local Variables
• A local variable: a variable defined inside
a method.
• Scope: the part of the program where
the variable can be referenced.
• The scope of a local variable starts from
its declaration and continues to the end
of the block that contains the variable. A
local variable must be declared before it
can be used.
46. 46
Strings
• Strings are objects that are treated by
the compiler in special ways:
• Can be created directly using “xxxx”
• Can be concatenated using +
String myName = “John Jones”;
String hello;
hello = “Hello World”;
hello = hello + “!!!!”;
int year = 2008;
String s = “See you in China in “ + year;
48. 48
Arrays
• Array is used to store a collection of
data of the same type.
• Instead of declaring individual
variables, such as number0, number1, ...,
and number99.
• You declare one array variable such as
numbers and use numbers[0], numbers[1],
and ..., numbers[99] to represent
individual variables.
51. 51
Arrays
• When we need to access the array we
can do so directly as in:
for (int i=0; i<5; i++)
{
System.out.println( arrayName[i] );
} // end for
52. 52
Example
double[] myList = new double[10];
for (int i = 1; i < myList.length; i++)
{
myList[i]=i;
}
for (int i = 1; i < myList.length; i++)
{
System.out.println(i);
}
53. 53
Array Initializers
• Declaring, creating, initializing in one step:
double [] myList = {1.9, 2.9, 3.4, 3.5};
• This shorthand syntax must be in one
statement and it’s equivalent to the
following statements:
double [] myList = new double[4];
myList[0] = 1.9;
myList[1] = 2.9;
myList[2] = 3.4;
myList[3] = 3.5;
55. 55
Objects
data field 1
method n
data field m
method 1
(A) A generic object
...
...
State
(Properties)
Behavior
radius = 5
findArea()
Data field, State
Properties
Method,
Behavior
(B) An example of circle object
•An object has both a state and
behavior.
•The state defines the object, and the
behavior defines what the object
does.
56. 56
Classes
• Classes are constructs that define
objects of the same type.
• A Java class uses variables to define
data fields and methods to define
behaviors.
• Additionally, a class provides a special
type of methods, known as
constructors, which are invoked to
construct objects from the class.
57. 57
Classes
class Circle {
/** The radius of this circle */
double radius = 1.0;
/** Construct a circle object */
Circle() {
}
/** Construct a circle object */
Circle(double newRadius) {
radius = newRadius;
}
/** Return the area of this circle */
double findArea() {
return radius * radius * 3.14159;
}
}
Data field
Method
Constructors
59. 59
Constructors, cont.
•Constructor name is the same as the
class name.
•Constructors do not have a return type
—not even void.
•Constructors are differentiated by the
number and types of their arguments.
• An example of overloading
•If you don’t define a constructor, a
default one will be created.
60. 60
Constructors, cont.
•A constructor with no parameters is
referred to as a no-arg constructor.
•Constructors are invoked using the
new operator when an object is
created.
• Constructors play the role of
initializing objects.
61. 61
Example
public class Circle
{
public static final double PI = 3.14159; // A constant
public double r;// instance field holds circle’s radius
// The constructor method: initialize the radius field
public Circle(double r) { this.r = r; }
// Constructor to use if no arguments
public Circle() { r = 1.0; }
// The instance methods: compute values based on radius
public double circumference() { return 2 * PI * r; }
public double area() { return PI * r*r; }
}
62. 62
Declaring Object Reference
Variables
To reference an object, assign the
object to a reference variable.
To declare a reference variable, use
the syntax:
ClassName objectRefVar;
Example:
Circle myCircle;
65. 65
Accessing Objects
• Referencing the object’s data:
objectRefVar.data
myCircle.radius
• Invoking the object’s method:
objectRefVar.methodName(arguments)
myCircle.findArea()
66. 66
Visibility Modifiers and
Accessor/Mutator Methods
• By default, the class, variable, or
method can be accessed by any class
in the same package.
• public: The class, data, or method is
visible to any class in any package.
• private: The data or methods can be
accessed only by the declaring class.
The get and set methods are used to read
and modify private properties.
67. 67
Why Data Fields Should Be
private?
• To protect data.
• To make class easy to maintain.
68. 68
Example
public class Student {
private int id;
private BirthDate birthDate;
public Student(int ssn, int year, int
month, int
day) {
id = ssn;
birthDate = new BirthDate(year,
month, day);
}
public int getId() {
return id;
}
public BirthDate getBirthDate() {
return birthDate;
}
}
public class BirthDate {
private int year;
private int month;
private int day;
public BirthDate(int newYear,
int newMonth, int
newDay) {
year = newYear;
month = newMonth;
day = newDay;
}
public void setYear(int
newYear) {
year = newYear;
}
}
public class Test {
public static void main(String[] args) {
Student student = new Student(111223333, 1970, 5, 3);
BirthDate date = student.getBirthDate();
date.setYear(2010); // Now the student birth year is
changed!
}
}
69. 69
Instance
Variables, and Methods
• Instance variables belong to a specific
instance.
• Instance methods are invoked by an
instance of the class.
70. 70
Scope of Variables
• The scope of instance and class
variables is the entire class. They can be
declared anywhere inside a class.
• The scope of a local variable starts from
its declaration and continues to the end
of the block that contains the variable. A
local variable must be initialized
explicitly before it can be used.
71. 71
The this Keyword
• Use this to refer to the object that
invokes the instance method.
• Use this to refer to an instance data
field.
• Use this to invoke an overloaded
constructor of the same class.
72. 72
Example
public class Circle {
private double radius;
public Circle(double radius) {
this.radius = radius;
}
public Circle() {
this(1.0);
}
public double findArea() {
return this.radius * this.radius * Math.PI;
}
} Every instance variable belongs to an instance represented by this,
which is normally omitted
this must be explicitly used to reference the data
field radius of the object being constructed
this is used to invoke another constructor
![7
A Simple Java Program
public class HelloWorld {
public static void main(String[] args){
System.out.println(“Hello World!”);
}
}](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-7-320.jpg)
![12
Identifiers EXAMPLE
public class Test
{
public static void
main(String[] args)
{
int a = 20;
}
}
In the above Java code, we have 5
identifiers as follows:
• Test: Class Name
• main: Method Name
• String: Predefined Class Name
• args: Variable Name
• a: Variable Name](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-12-320.jpg)
![16
Variable Declaration
Example
public class DeclarationExample {
public static void main (String[] args) {
int weeks = 14;
long numberOfStudents = 120;
double averageFinalGrade = 78.6;
char ch=‘a’;
System.out.println(weeks);
System.out.println(numberOfStudents);
System.out.println(averageFinalGrade);
System.out.println(ch);
}
}](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-16-320.jpg)
![44
public class TestMethodOverloading {
/** Main method */
public static void main(String[] args) {
// Invoke the max method with int parameters
System.out.println("The maximum between 3 and 4 is "+ max(3, 4));
// Invoke the max method with the double parameters
System.out.println("The maximum between 3.0 and 5.4 is"+ max(3.0,5.4));
}
/** Return the max between two int values */
public static int max(int num1, int num2) {
if (num1 > num2)
return num1;
else
return num2;
}
/** Find the max between two double values */
public static double max(double num1, double num2) {
if (num1 > num2)
return num1;
else
return num2;
}
}](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-44-320.jpg)
![48
Arrays
• Array is used to store a collection of
data of the same type.
• Instead of declaring individual
variables, such as number0, number1, ...,
and number99.
• You declare one array variable such as
numbers and use numbers[0], numbers[1],
and ..., numbers[99] to represent
individual variables.](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-48-320.jpg)
![49
Arrays
5.6
4.5
3.3
13.2
4
34.33
34
45.45
99.993
11123
double[] myList = new double[10];
myList reference
myList[0]
myList[1]
myList[2]
myList[3]
myList[4]
myList[5]
myList[6]
myList[7]
myList[8]
myList[9]
Element value
Array reference
variable
Array element at
index 5](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-49-320.jpg)
![50
Arrays
• Declaring Array
• dataType [] arrayRefVar;
• Example:
• int[] arrayName;
• Creating Arrays
− arrayRefVar = new dataType[arraySize];
• Example:
− arrayName = new int[5];](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-50-320.jpg)
![51
Arrays
• When we need to access the array we
can do so directly as in:
for (int i=0; i<5; i++)
{
System.out.println( arrayName[i] );
} // end for](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-51-320.jpg)
![52
Example
double[] myList = new double[10];
for (int i = 1; i < myList.length; i++)
{
myList[i]=i;
}
for (int i = 1; i < myList.length; i++)
{
System.out.println(i);
}](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-52-320.jpg)
![53
Array Initializers
• Declaring, creating, initializing in one step:
double [] myList = {1.9, 2.9, 3.4, 3.5};
• This shorthand syntax must be in one
statement and it’s equivalent to the
following statements:
double [] myList = new double[4];
myList[0] = 1.9;
myList[1] = 2.9;
myList[2] = 3.4;
myList[3] = 3.5;](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-53-320.jpg)
![68
Example
public class Student {
private int id;
private BirthDate birthDate;
public Student(int ssn, int year, int
month, int
day) {
id = ssn;
birthDate = new BirthDate(year,
month, day);
}
public int getId() {
return id;
}
public BirthDate getBirthDate() {
return birthDate;
}
}
public class BirthDate {
private int year;
private int month;
private int day;
public BirthDate(int newYear,
int newMonth, int
newDay) {
year = newYear;
month = newMonth;
day = newDay;
}
public void setYear(int
newYear) {
year = newYear;
}
}
public class Test {
public static void main(String[] args) {
Student student = new Student(111223333, 1970, 5, 3);
BirthDate date = student.getBirthDate();
date.setYear(2010); // Now the student birth year is
changed!
}
}](https://image.slidesharecdn.com/javabasics-250623174745-6556d567/85/Java-basics-includes-java-classes-methods-OOPs-concepts-68-320.jpg)
