Session - 1

Introduction to

Introduction

• Humans need languages to communicate with each other,
• Similarly we need a language to communicate with the computers.
• Programming languages are used to communicate with the computer
• Java was introduced in 1991 by Sun Microsystems

• James Gosling from Sun Microsystems and his team were working on the first version of java.

• Later it was taken over by ORACLE.
• First it was named as Oak, then they got to know a programming language called Oak already exists.
• Later it was named as JAVA.

Why do we need to use Java ?

Why do we need to use Java?

• Java is a very powerful language.
• Java is platform independent that means that you can run the same program on Windows, Linux, MAC OS etc.
• Platform independent means that you write code any one platform but the code can be executed in all the platforms.

Java Program written in OS

Why do we need to use Java?

• It is an object oriented language with features like inheritance, polymorphism, encapsulation, abstraction.
• It is secure since it runs programs in a sandbox.
• You can carry out multiple operations in parallel.
• You can make your own applications like calculators , games etc, manage data in the database and also contribute to the open source world through Java.

Online editors

Class_name:

​

They are case-sensitive, so name them carefully. For better practice start it with capital letter and you can use other symbols and numbers. It can be of any length.

And most important make sure the name you are giving to your class is not a keyword in java.

​

public static void main(String[] args):

​

Main function declaration, the code inside main function is where the execution of the program starts.

Your first Java code

Click on Execute to run the Code

• When we type something in word document we have enter key, tab key, space key etc to make proper spacing.
• When we do the same thing in a java program we need something to play with space.
• So we have escape sequence.

Escape characters Java

What are Data Types :

• Data types are keywords which indicate the type of value a variable will hold.
• It can be string, integer, float ….etc.
• We can choose different types of variable names to store the values.
• The names should start with lowercase letters and it can have numbers.

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Java Variables

• A variable is a container which holds the value while the Java program is executed. A variable is assigned with a data type.
• Variable is a name of memory location. There are three types of variables in java:

local, instance and static.

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NOTE : When we write a statement with a data type and a variable

it reserves space in memory to store the value.

This is the declaration of the variable.

​

int i=10;

​

10

Type :int / integer

Name of variable : i

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Operators in Java

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Types of operators in java

• Arithmetic operator
• Comparison operators
• Logical operators
• Bitwise operators
• Ternary operators
• Increment operator
• Decrement operator

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Arithmetic Operators

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Code for Arithmetic operator

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Comparison operator

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Code for comparison operator

Comparison operator always returns a Boolean value

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Logical Operators

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Code for Logical operator

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�Ternary operators�

Ternary operator works just like if else statements if the first condition is true it prints the statements else it goes for else part.

Syntax: variable=Expression1?Expression2:Expression3

If the Expression 1 is true it will assign the Expression 2 to the variable or else it assigns Expression 3 to the variable.

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Code for Ternary operator

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Increment operator

Increment operator is used to increase the value by one

Symbol:++

​

We can use increment operator(++) as prefix and postfix.

1. If you use the ++ operator as prefix like ++variable. The value of variable is incremented by 1 then, it returns the value.
2. If you use the ++ operator as postfix like variable++. The original value of variable is returned first then, age is incremented by 1.

​

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Code for Increment operator

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Decrement operator

Decrement operator is used to increase the value by one

Symbol: --

​

We can use increment operator(--) as prefix and postfix.

1. If you use the -- operator as prefix like --variable. The value of variable is decremented by 1 then, it returns the value.
2. If you use the -- operator as postfix like variable--. The original value of variable is returned first then, age is decremented by 1.

​

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Code for Decrement operator

After post fix what happens to the value b?

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Java Control Statements

Java Session 4

IF – then Statement

• IF - then Loop is a basic of control flow statements.
• IF the condition is satisfied then the commands in the brackets is executed.
• Syntax

if(condition)

{

Statements;

}

Flowchart for IF-then

Condition

True

False

True Statements

Continue with the rest of the code

Code for If -then

IF ELSE Statement

After you write your exams your are awarded grades for that. Grades are awarded according to the marks scored in this way.

Flowchart for if else loop

Marks

is equal to condition

True

False

True statements

False statements

Code for if–else loop

IF-ELSE-IF LOOP

After you write your exams your are awarded grades for that. Grades are awarded according to the marks scored in this way.

Syntax for IF-ELSE-IF loop

If(condition)

{

statement;

}

else if(condition)

{

statement;

}

….

….

….

else

{

statement;

}

_{Flow chart for if -else-if loop}

_condition

_True

_false

_Condition

_True

_false

_{True statements}

_{True statements}

_{False statements}

Code for IF-ELSE-IF LOOPS

Switch Case

Switch case is similar to the if else loop:

​

1. Switch expression is evaluated once.
2. The value of expression is compared with the value of each case, if it matches then the associated block of statements is executed.

Syntax for Switch case

switch(expression/ value)

{

Case x : code block;

Break;

Case y : code block;

Break;

……

……

Default: code block;

Break;

}

Note:

Break and Default are keywords in switch - case.

Break : when a match is found, execution will stop and program breaks out from the switch case loop.

Default : It is executed only if there is no case match.

Flowchart for Switch case

Code for switch case

Loops using GUI

�FOR Loops In Java using GUI�

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What is Loop?

• In programming language Loops are used to repeat the statement until a particular condition is satisfied.

Example: Monkey jumping 3 times in a Loop

After jumping 3 times it will exit the loop

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For loop

• When we know the exact number of times the Loop has to be executed then we can use a FOR loop.
• A range of values can be specified in a FOR Loop.

Flow chart for FOR loop

condition

Statements

Increment/decrement

Stop

false

true

Design a square using FOR loop

Activate the pen with size 10

Set the loop to repeat for 4 times

Move the pen forward 100 units and turn 90 degrees

Fill the shape with yellow color

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Design a flower using for loop

Activate the pen with size 3

Set the loop to repeat for 10 times

Make an Arc with radius 100

Turn Left to draw another Arc

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Design a Square Spiral using FOR Loop

Activate the pen with size 3

Set the loop to repeat for 40 times

Move the pen forward

x * 5 units and turn 90 degrees

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What is Nested for loops

• If a loop exists inside the body of another loop, it’s called a nested loop. Here’s an example of the nested loop.

Design the shape using Nested for loops

output

What is IF loop

• IF Loop is the basic loop of control flow statements.
• If the condition is true then block of statements are executed.

Loop to draw different polygons using if statements

What is if else loop

• If – then – else loop is used to provide the alternate path if the condition is false.
• Example

If(condition)

{

statements;

}

else

{

statements;

}

​

Program for if else

What is nested if else if loop

• If -else- if loop is used to execute when the condition is false check for another condition.

If(condition)

{

statements;

}

else if(condition)

{

statements;

}

else if (condition)

{

statements;

}

Program for nested if

Output

Loops in java

While loop

• While Loop continually executes the block of statements as long as the condition is true. Once condition is false it will break out of the Loop.

​

Syntax for while loop:

While (condition)

{

Statements to be executed;

}

Flow chart for While Loop

start

Statements

Exit Loop

stop

condition

true

false

How while Loop works

int i=0;

While(i<3)

{

System.out.println(“Hi”);

i++;

}

0

true

Storage container

int

i

Output

condition result

condition

increment

Hi

Hi

Hi

1

true

2

3

false

Code for while loop

For loop

​

• When we know the exact number of times the Loop has to be executed then we can use a FOR loop.
• A range of values can be specified in a FOR Loop.

Syntax for FOR Loop

for(initialization; condition; increment / decrement)

{

code inside the loop;

…….;

…….;

…….;

}

Flow chart for FOR loop

condition

Statements

Increment/decrement

Stop

false

true

How for Loop works

for(int i=0;i<3;i++)

{

System.out.println(“Hi”);

}

0

true

Storage container

int

i

Output

condition result

condition

increment

Hi

Hi

Hi

1

true

2

3

false

Code for For loop

��Java program to print the sum of first 20 natural numbers�

Program for factorial

• The factorial function (symbol: !) says to multiply all whole numbers from our chosen number down to 1. 
• 7!=7x6x5x4x3x2x1
• Factorial zero is equal to 1.

Do while

​

​

• Do while is a variant of the while Loop.
• The condition is given at the end of the loop, so the loop will get executed at least once.
• Rest of the functionality remains the same as while loop.

​

​

Syntax for do while

do

{

loop statements;

loop statements;

…;

…;

}while(condition)

Flow chart for do while loop

statements

condition

stop

false

True

How do while works

int i=0;

do{

System.out.println(“Hi”);

i++;

}while(i<3)

0

true

Storage container

int

i

Output

condition result

condition

increment

Hi

Hi

Hi

1

true

2

3

false

How do while works

int i=4;

do{

System.out.println(“Hi”);

i++;

}while(i<3)

4

Storage container

int

i

Output

condition result

condition

increment

Hi

5

false

Code for do while loop

Functions in Java

Functions

• What is a Function?

Function is a self contained block of statements which performs a particular task. In java functions are also called as methods.

​

• How it is useful in real-time?

when we are doing some actions we can take few actions as procedure and give it a name.

​

​

Syntax for declaring functions

Access specifier Access modifier void methodName()

{

​

Code to be executed //method implementation

……..

}

Access specifier= public or private

Access modifier =static or non static

​

• We have to create functions/methods always in inside the class.
• Function/Methods are created for reusability and to identify errors quickly.
• We can declare methods, before creating the main method because JVM always executes the main method first.

​

Sample program

• In the above sample program execution starts from main method
• When test1 method is called it goes to the test1 method and executes the test1 implementation and returns to the main method.
• When test2 method is called it goes to the test2 method and executes the test2 implementation and returns to the main method.
• And finally executes the final statements in the main method.

​

Function returns a value

Syntax:

Access specifier access modifier returntype method/function name()

{

----------------

----------------

.

.

.

----------------

}

Implementation

1. In the above syntax , if the function has to return integer then the return type should be int.
2. if the function has to return string then the return type should be string.
3. If the function has to return double then the return type should be double.

​

Sample program

Function with Parameters

1. We can pass the data to the functions as parameter. Parameters acts as variables.
2. Parameters are specified after the method name inside the ()”parentheses”. You can pass as many as you want by separating with comma “ , ” .

Sample program

In the above program

X and Y are called as Arguments.

a and b are called as parameters.

Scanner

• Scanner class is used to get the input from the user. To work with the scanner class import java.util.Scanner;
• To use the Scanner class, create an object of the scanner class and use available methods present in the scanner class

Methods available in scanner class

Sample Program

Sample Program 2

Calculator Project

• Basic functionality of a calculator is to
• ADD
• SUBTRACT
• MULTIPLY
• DIVIDE

​

• Let us design a Calculator which takes 2 numbers from the user and the operation and performs the calculation.

Calculator Project

Input & Output Operations

To use Mathematical Operators

To take input from users

Define your main method inside the Calculator class

Calculator Project

Declaring to variables to store number

This command helps us for user input

Take Operation Input

Calculator Project

Here we used switch-case

Based on the operator selected the operation is carried out on the numbers

Calculator Project

Calculator Project Output