Day 02 - 28 Aug - Java.md

Day 02 - 28 Aug

Java Editions

Java was initially developed by Sun Microsystems and released as open source software under the GNU General Public License (GPL). Now java is a product of Oracle Corporation. There are four editions of java are available:

• Standard Edition (SE)
• Micro Edition (ME)
• Enterprise Edition (EE)
• Card Edition (CE, Learn more about it from wikipedia)

Usage of Package in Java

A package can be used for grouping classes and interfaces together that share a common purpose or concern. It contains all related programs.

Basic Structure of All Java Program

// Optional package declaration
package com.example.myprogram;

// Import statements (if needed)
import java.util.*;

// Class declaration
public class MyClass {
    // Main method
    public static void main(String[] args) {
    // Program statements
        System.out.println("Hello, naztech!");
    }

    // Other methods (if needed)
    // ...
}

Note: Java file name must be same as class name, which identify as main class In a single java file, main class must be public Must have a main method to main class to start executing a program

📝Practical

Program Practice

HelloWorld.java: A program to print "Hello, World"

public class HelloWorld {
	public static void main(String[] args){
		System.out.println("Hello, World");
	}
}

UserInput.java: Write a program that take user input to show some output

import java.util.Scanner;

public class UserInput {
	public static void main(String[] args) {
		Scanner myScanner = new Scanner(System.in);
		System.out.print("What is you name?: ");
		
		String name;
		name = myScanner.nextLine();

		// Output: Welcome, {Inputed name}
		System.out.println("Welcome, " + name);
	}
}

CommandLineArg.java: Write a program to show some text by command line arguments.

public class CommandLineArg {
	public static void main(String[] args) {
		System.out.println(args[0] + " " + args[1] + " " + args[2]);
	}
}

✍ Class Test

10 Reserved Words of Java

if, else, try, catch, finally, for, do, while, class, public, protected, private etc.

Data Types

• Char - char
• String - String
• Byte - byte
• Boolean - bool
• Integer - int
• Double - double
• Float - float
• Short - short

Access Modifes in Java

• default
• public
• protected
• private

5 Valid Variable Names in Java

• name
• name2
• $name
• _name
• full_name