In this page, we will learn about the basics of OOPs. Object-Oriented Programming is a paradigm that provides many concepts, such as inheritance, data binding, polymorphism, etc.

Aptech Software Ltd.
Session 2
Java Language Fundamentals

A Simple Approach – Core Java / Session 2/ 2 of 30
Review
 Java was introduced by Sun Microsystems in 1995.
 Java is object-oriented and a cross platform language.
 Java bytecodes are machine language instructions understood by
the Java Virtual Machine (JVM) and usually generated as a result of
compiling Java language source code.
 A "Just-In-Time" (JIT) Java compiler produces native code from
Java byte code instructions during program execution.
 Applets are Java programs that run through a Java enabled web
browser.The Java Development Kit (JDK) contains the software and
tools needed to compile, debug and execute applets and
applications written in the Java language. It’s basically a set of
command-line tools.
 Java program can be run using command-line arguments.
The data type of these arguments is String.

Objectives
Explain the basics of Java Language
Identify the Data Types
Understand arrays
Identify Operators
Format output using Escape Sequence
Use Control Flow Statements

Basics of the Java Language
Data types Variables Operators Control Flow Statements
Java Blocks
A variable is a named memory location.
Data types determine the type of data to be stored in memory.
An operator is a symbol that operates on one or more arguments to
produce a result.
Programs are executed in sequential order. Control flow statements allow
variations in this sequential order.

Data Types
 byte
 char
 boolean
 short
 int
 long
 float
 double
 Array
 Class
 Interface
Primitive Data Types Reference Data Types

Variables
Three components of a variable
declaration are:
 Data type
 Name
 Initial value to be assigned (optional)
Syntax:
datatype identifier [=value][,
identifier[=value]...];

class VariableTest {
public static void main(String [] args) {
double a = 1.0;
int b = 3;
System.out.println("Value of double variable is: "+a);
System.out.println("Value of integer variable is: "+b);
}
}
Variable declaration and
initialization
Example
Note: Always initialize your variables when you define
them. If you don’t know what value a variable should have
when you define it, initialize it to zero.
float f;

Scope and Lifetime of Variables
Variables can be declared inside a block.
The block begins with an opening curly brace
and ends with a closing curly brace.
A block defines a scope.
A new scope is created every time a new block
is created.
Scope specifies which variables are visible to
other parts of the program.
It also determines the life of the variables.

class ScopeVariable {
public static void main(String[] args) {
/* num is available in inner scope */
int num = 2;
/* Testing variable num */
if (num == 2) {
int num1 = num * num;
System.out.println("Value of num and num1 are "
+ num + " " + num1);
}
/* num1 = 10; ERROR ! num1 is not known */
System.out.println("Value of num is " + num);
}
}
Example
//num1 = 10; ERROR ! num1 is not known
 Check the scope of the variables.
 ERROR!!! If variable is accessed outside its scope.

Type Casting
Type Casting causes the program to treat a
variable of one type as though it contains data
of another type.
Example:
float c = 34.89675f;
int b = (int) c + 10; // Convert c to an integer

Types of Data Conversion
Automatic Type Conversion Casting
When one type of data is assigned
to a variable of another type,
automatic type conversion takes
place provided it meets the
following conditions:
The two types are compatible.
The destination type is larger
than the source type.
Casting is used for explicit type
conversion. It loses information
above the magnitude of the
value being converted.

Example
 Declare and initialize the variables
 Add the variables and assign the
value to the variable of different
data type without explicit type
casting.
 No ERROR!!!
long sum;
int first = 20,
second = 30;
sum = first + second;
Demonstration: Additional Example 2
Automatic Type Casting Casting
 Declare the variables
 The variables will hold the
values which are passed
during runtime.
 Add the variable after type
casting.
int first, second, sum;
first = Integer.parseInt(args[0]);
second = Integer.parseInt(args[1]);
sum = first + second;

Type Promotion Rules
All byte and short values are promoted to int
type.
If one operand is long, the whole expression is
promoted to long.
If one operand is float, the whole expression is
promoted to float.
If one operand is double, the whole expression
is promoted to double.

Arrays 1-2
 An array is a data structure that stores data of same data
type in consecutive memory locations.
 Three ways to declare an array are:
datatype identifier [ ];
datatype identifier [ ] = new datatype[size];
datatype identifier [ ] = {value1,value2,….valueN};
 Array can have more than one dimension

Arrays 2-2
 It consists of a single
column of data of the
same type.
 An array is declared
by specifying its name
and size.
One Dimensional Array Multi Dimensional Array
 Multi Dimensional arrays are
arrays of arrays.
 To declare a Multi Dimensional
array, additional index has to
be specified by using another
set of square brackets.

Example
 Array Declaration
 Accessing the array elements
 Using the length property
Demonstration: Example 3 and Additional Example 3
/* Array Initialization */
double[] nums = {2, 0, 1};
/* Printing array element */
System.out.println("The value at location 3
is :" + nums[2]);
int[] numbers = {8, 18, 5, 2, 1, 10};
System.out.println("Total number of
elements in an array is: "+ numbers.length);
System.out.println("First element in an
array is: " + numbers[0]);
System.out.println("Last element in an
array is: “ + numbers[numbers.length - 1]);

Operators
Operators Description Examples
Arithmetic
Operators Arithmetic Operators use numeric operands. These
operators are mainly used for mathematical calculations.
+, - * % etc
Relational
Operators
Relational Operators test the relation between two operands.
The result of an expression where relational operators are
used is boolean.
==, >=, <= etc
Logical
Operators
Logical Operators work with boolean operands. &, |, ^ etc
Conditional
Operators
The Conditional Operator is unique, because it is a ternary
or triadic operator that has three operands to the expression.
It can replace certain types of if-then-else statements.
!=, =, *=, /=, +=, -=
Assignment
Operators
The Assignment Operator is a single equal sign, =, and
assigns a value to a variable.
=

Examples
Code Snippet:
int a= 5, b= 12,d=10,c;
c=a+b; Addition
c=a%b; Modulus
d++; Increment
d--; Decrement
Value of c and d:
c=17 After adding
c=2 This is remainder of a/b
d=11 After incrementing
d=10 After decreasing the value
Code Snippet:
boolean i=true, j=false;
boolean or=i|j, and=i&j;
!i;
!j;
Value of or and and:
or=true Using logical or
and=false Using logical and
i=false Using logical unary not
j=true Using logical unary not
Arithmetic Operators Logical Operators

Operator Precedence
 Expressions that are written will generally consist of several
operators. The rules of precedence decide the order in which
each operator is evaluated in any given expression.
Order Operator
1. Parentheses like ( ) and [ ]
2. Unary Operators like +, -, ++, --, ~, !
3. Arithmetic and Shift operators like *, /, %, +, -, >>, <<
4. Relational Operators like >, >=, <, <=, ==, !=
5. Logical Operators like &, ^, |, &&, ||
6. Conditional and Assignment Operators like ?=, =, *=, /=,
+=, -=

Formatting output with Escape Sequences
 Whenever an output is to be displayed on the screen, it needs to be
formatted.
 The formatting can be done with the help of escape sequences that
Java provides.
Example:
System.out.println (“Happy tBirthday”);
Output:
Happy Birthday

Control Flow Statements
 All application development environments provide a
decision making process called control flow statements
that direct the application execution.
 Control flow enables a developer to create an
application that can examine the existing conditions,
and decide a suitable course of action.
 Loops or iterations are an important programming
construct that can be used to repeatedly execute a set
of actions.
 Jump statements allow the program to execute in a non-
linear fashion.

Types of Control Flow Statements
Decision-making
if-else statement
switch-case statement
Loops
while loop
do-while loop
for loop

if-else statement
 The if-else statement tests the result of a condition,
and performs appropriate actions based on the result.
 It can be used to route program execution through two
different paths.
 The syntax of if-else statement is::
if (condition)
{
action1;
}
else
{
action2;
}

switch – case statement
 The switch – case statement can be used as an alternative for if-else-if
statement.
 It is used in situations where an expression is evaluated multiple values.
 The use of the switch-case statement results in better performance.
 The syntax of switch-case is:
switch (expression) {
case 1:
action1 statements;
break;
case 2':
action2statements;
break;
….
case N ':
actionN statements;
break;
default:
default statements; }

Loops 3-1
while
The while loop executes a statement or set of statements as long as the
condition specified evaluates to true.
Syntax
int count = 0;
while (count < 10) {
System.out.println(count);
count++;
}
Example
while (test)
{
// statement
}
Executed
Condition = True

Loops 3-2
do-while
The do-while loops execute certain statements till the specified condition is
true. This loop ensures that the loop body is executed at least once.
Syntax
do {
System.out.println(count);
count++;
} while (count < 10)
Example
do {
//statement
}while (test)
Executed
Condition = True

Loops 3-3
for
The for loop is primarily used for executing a statement or block of statements a
predetermined number of times.
Syntax
For(count = 0; count
<10; count++) {
System.out.println(coun
t);
}
Example
for(initialization;test;
increment){
action statements;
}
Condition = True
Executed

Jump Statements 2-1
 Two jump statements are:
break
continue
break statement: It is used to terminate the block.
continue statement: Sometimes the programmer might
want to continue a loop, but stop processing the
remainder of the code in its body for a particular iteration.
The continue statement can be used for such an action.

Jump Statements 2-2
 Introduce break keyword in the loop.
 Avoid Unnecessary execution.
 Terminate the loop.
int number = 41;
int is_prime = 1;
for(int i = 2; i * i <= number; i++) {
if((number%i)==0){
is_prime = 0;
break;
}
}
if(is_prime==1) {
System.out.println("It is a prime number");
}
else {
System.out.println("Not a prime number");
}
}

Summary
 Java has built-in data types, known as primitive data types.
 Variables are basic units of storage.
 Casting is a facility of converting a data type to another data type.
 Arrays are used to store several items of same data type in consecutive
memory locations.
 Java provides different types of operators. They include:
 Arithmetic
 Relational
 Logical
 Conditional
 Assignment
 Java supports the following programming constructs for the control
statements:
 if - else
 switch
 for
 while
 do - while
 The two jump statements, break and continue, help to transfer control to
another part of the program.

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