Java Tutorial 1


Java Tutorial 1
(Java Environment Setup and Write First Java Program)
> Download Java (JDK) Software and Install

> set Environment Variable (Path Variable)
(* If want to execute Java programs from any directory in C Drive)

How to set Path Environment Variable:
OS: Windows 7

> Select MYComputer and Right click

> Properties

> Advanced System Settings

> Environment Variables

> Select "New" in System variables

> Enter Variable as "Path"

> Enter JDK bin directory path ("C:\Program Files\Java\jdk1.8.0_45\bin") in value field

> OK > OK > Ok
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Verify the Environment setup:
> Launch Command Prompt

> Type java (It provides details)
-------------------------------------
Three steps to write and execute Java Programs

i) Write Java Program in Notepad (Editor)

ii) Compile the Program (It creates Class file)

Command prompt > Change to Program file Directory

> Type javac Programname.java (java is extension of Java program, javac command for compilation)

iii) Run /Execute the Java Program

> Type java programName
(It provides Output on the console)
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Use Eclipse IDE to write and execute Java programs.
Eclipse IDE (Integrated Development Environment)

It is a platform to write and execute Java programs, Perl, Python, PHP, Ruby etc...

It provides Editor, context help, help for syntax errors, Auto compilation and debugging.
-----------------------------
Download Eclipse software and extract.

Steps:
----------------
> Create Java Project
    -> Create a Package
        -> Create a Class / Interface
(We can write java code in the Class file)
--------------------------------------

Ex:
public class Sample {
    public static void main (String [] args){
        System.out.println("Hello Java and Selenium");
    }
}
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Java Program structure or Java Syntax:
 

1) Package declaration statement
ex:

package abcd;
--------------------------------
2) Import statements
we can import Built in and User defined Libraries using import keyword.
(In order to use Existing Classes, Objects, and Methods)


Example:

import java.io.console;

(It Imports Console Class only from io package)

import java.io.*;

(It imports all classes from io package)
------------------
java - project

io - package

Console - Class
----------------------------------------------
3) Class declaration statement
ex:

public class Sample {
}

public - Access Modifier

class - Java keyword to declare a class

Sample - Name of the Class

Note: First letter of Class name should be upper case.
-------------------------------------------------
4) Comments section
// This is a Sample Java Program
-----------------------------------
5) Main Method  

(Java program execution starts from main method.)
(Main method is mandatory in every Java program)

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

public - Access Modifier

static - use main method without invoking any object.

void - returns nothing

main - method name
-------------------------------------------
6) Declarations
We can declare variables and constants
-----------------------------
Normal statements

Conditional blocks

Loop blocks

Method declarations

Etc...
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Sample Java Program:
package abcd;

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

public class Sample2 {
    // This is a Sample Java Program
    public static void main (String [] args){
        int a = 50, b, c; // Declaration of Variables
        b= 20; // Initialization
        System.out.println(a + b); // 70
        System.out.println("Addition of a, b is: "+ (a+b));
        final int MONEY = 100; // Declaration of Constant
       
        if (a > b) {
            System.out.println("A is a Big Number");
        }
        else
        {
            System.out.println("B is a Big Number");
        }   
       
        for (c = 1; c <= 10; c++){
            System.out.println(c);
        }
        }
    }

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