Java Program Structure and Java Syntax

Java Program Structure and Java Syntax

i) Java Program Structure

ii) A Sample Java Program

iii) Comments in Java

iv) Java Data Types
—————————————–
Java Environment Setup

> Download Java (JDK) Software and Install

> Set Environment Variable (Path variable)

> Download Eclipse IDE and Extract.
————————–
Create Java project
> Create Java Package
Create Java Class /Program
—————————————–
i) Java Program Structure

1) Documentation Section

2) Package declaration Statement

Ex: package xyza;

3) Import Statements

We import built in and User defined libraries using import keyword

Ex:

import java.io.Console;
import java.lang.*;

import – It is a Java keyword to import Libraries.

java -Project

io -Package

Console – Class

lang.*; – import all classes from lang package.
————————————–
4) Class declaration Statement

public class Sample {

}

public – Access Modifier

class – Java keyword to declare a class

Sample – it is the Class name (You can use any meaningful name)
———————————————-
5) main Method (Java Program execution starts from main method)
(* It is the mandatory statement in every Java program)

public static void main (String [] args) {
}

public – Access Modifier

static – Non-Access Modifier (use main method without invoking any object)

void – Returns nothing

main- method name
———————————–
6) Declarations

We can Declare Variables and Constants.

Other Statements

System.out.println(“Hello Selenium”);

System – Class (Pre-defined)

out – Object

println – method

“Hello Selenium” – Message
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7) Code blocks

Condition blocks

Loop blocks

Method blocks (method declaration before the main method, but we access methods after main method)
etc…
————————————-
> Every normal statement/step ends with semi colon

> Every code block enclosed with {}
—————————————–
ii) A Sample Java Program

//Documentation

package xyza;

import java.io.Console;
import java.lang.*;

public class Sample {

//Create a Method(User defined)
public int multiply(int a, int b, int c){
int result = a * b * c;
return result;
}

public static void main (String [] args){
// This is a sample Program

int a = 10, b, c; //Variables Declaration
b = 20; c = 30; //Initialization

final int money =100;//Constant Declaration

System.out.println(“Addition of a, b is ” + (a + b));//Addition of a, b is 30
System.out.println(money);//100
System.out.println(c);//30

//Condition Block
if (a > b){
System.out.println(“A is a Big Number”);
}
else
{
System.out.println(“B is a Big Nuber”);
}

//Loop block

for (int d=1; d <=10; d++){
System.out.println(d);
}
//Create Object and access Methods
Sample obj = new Sample();
int x = obj.multiply(10, 25, 50);
System.out.println(x);
}
}
—————————————–
iii) Comments in Java

Comments are English words used for Code documentation.

Purpose of Comments

a) To make the code Readable

b) To make the code disable from execution
————————
Comments Syntax in Java

Use // for Single line comment

Use /* ……
………..
…………..
*/ for multiple lines comment

Example:
package xyza;

public class Sample2 {

public static void main (String [] args){
//This is a Sample Program
int a, b, c; //Declaration of variables
a=10; b=20;c=30;

/*if (a > b){
System.out.println(“A is a Big Number”);
}
else {
System.out.println(“B is a Big Number”);
}*/

System.out.println(c);
}
}
————————————
Usage of Comments in Test Automation

a) To write Test Case header

b) To write Method header

c) To explain complex logic etc…
—————————————–
iv) Java Data Types

Data Type is a classification of the type of data that variable or Constant or object can hold in computer programming.

Ex: character, integer, float, boolean etc…

Java Supports Explicit Declaration of Data Types.
(we need to specify the data type before declaring the a Variable or constant etc….)

Syntax:

dataType variableName;

dataType variableName =value;

dataType variable1Name, variable2Name, variable3Name;

Example:

int a;

char b =’A’;

int a, b, c;
—————————–
Two Types of data Types in Java

a) Primitive Data Types

b) Non-primitive Data Types / Reference Data Types
——————————–
a) Primitive Data Types (8 data types)

i) Integer Types
—————-
1) byte (8 bits)

byte a =10;

2) short (16 bits)

short a =10000;

3) integer(32 bits)

int a = 100000;

4) long (64 bits)

long a =100000000000000;
————————
ii) Relational types (Numbers with decimal places)

5) float (32 bits)

float a = 1.23;

6) double (64 bits)

double a =123.345654322;
——————————-
iii) Characters

7) character

char a =’Z’
—————————-
iv) Conditional

8) Boolean

boolean a = true;
——————————
b) Non-primitive Data Types / Reference Data Types

Non-primitive or Reference data types in Java are Objects and Arrays.

ex:

Button a = new Button(“OK”)
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(1899)

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