Class Room Notes and Examples

React JS Test

https://forms.gle/nxLYUZV8JUFaZAVA9

MCQs Week - 8

https://forms.gle/aGpUajx7vnnLpvbS6

Remaks on Module 1 Test

https://docs.google.com/spreadsheets/d/1fxR5cZUn6voCuHE14wpqomHTi-SxC2ewV6UKryEYd4U/edit?usp=sharing

Maven Download

https://dlcdn.apache.org/maven/maven-3/3.9.1/binaries/apache-maven-3.9.1-bin.zip

SonarQube Download

https://binaries.sonarsource.com/Distribution/sonarqube/sonarqube-8.9.10.61524.zip

MySQL Installation Guide

https://dev.mysql.com/doc/refman/8.0/en/windows-install-archive.html

Daily Retrospective :

Daily Retrospective Link

4ls

4Ls Link

Important Links

• Core Java - Overview, First Java Program, Variables, Datatypes, Literals, Operators, Expressions and Conditional Statements. https://www.geeksforgeeks.org/java-programming-basics/
• Core Java - String, Arrays, Looping Statements, Methods, Class, Object, static https://www.programiz.com/java-programming
• Core Java - Access Modifiers, Packages, Encapsulation https://www.javatpoint.com/inheritance-in-java
• Core Java - Polymorphism, Inheritance, Abstraction, Interface https://www.geeksforgeeks.org/polymorphism-in-java/
• Core Java - Collection Framework, ArrayList, Map, Set. https://www.geeksforgeeks.org/collections-in-java-2/
• Core Java - File Handling, Threads and Garbage Collections, Exception Handling, Enums. https://www.javatpoint.com/java-io
• Java 8 - Java 8 Features - Lambda Expressions, Streams, Filters, java.time. https://www.journaldev.com/2389/java-8-features-with-examples
• Junit 5 and Maven - Writing basic tests, Assert Statements, Testing Exceptions https://howtodoinjava.com/junit-5-tutorial/
• RDBMS - DDL Commands, DML Commands https://www.javatpoint.com/mysql-tutorial
• RDBMS - Operators, Aggregate, String, Date Functions https://www.geeksforgeeks.org/sql-tutorial/
• Web Basics - Learn the basics of HTML5 & CSS3 https://www.w3schools.com/html/
• JavaScript - Learn the basics of Javascript https://www.javatpoint.com/javascript-tutorial

Day 1

M1 - Java + SQL + GIT

M2 - Web(Client Side)

• HTML CSS JS Bootstrap Angular

M3 - Web(Server Side)

• Java EE, Spring, Microservices, Docker

M4 - Cloud and Deployment

• AWS, Kubernetes, CICD, DevOps

M5 - Project

M6 - Advanced Concepts (Cloud, DevOps, Testing)

What is Java?

Java - Object Oriented Programming Language

Java Dev Setup

• JDK
• JAVAC - Java Compiler
• Runtime Libraries
• JVM - Java Virtual Machine

Writing our 1st Java Program

class Program{
  public static void main(String []args){
	System.out.println("UST Global");
  }
}

• Program.java

• javac Program.java -> Compile

• Program.class -> Byte code

• java Program -> Executing the code

• Program 1:

class Program{
  public static void main(String []args){
	String companyName = "UST Global";
	System.out.println(companyName);
  }
}

• Program 2 :

class Program{
  public static void main(String []args){
    String message = "Hello everyone";
	String companyName = "UST Global";
	System.out.println(message+", welcome to "+companyName);
  }
}
// Hello everyone, welcome to UST Global

How to store numbers:

• Integer : int

• Program 3:

class Program{
  public static void main(String []args){
    	int num = 10;
	System.out.println(num);
  }
}

Day 1 Retrospective

---

What did we learn?

---

• What is Java?
• Why Java?
• How to write Java Program
• How to compile and run java code

Any challenges?

---

• Software setup issues
• Network Connection issues

What is there for tomorrow?

---

• Variables and Data Type
• SDLC and Program Flow

Day 2 Standup :

What did we complete yesterday?

What are we going to do today?

• Understand the Software Development Lifecycle
• Understand the difference between Waterfall and Agile Model
• Understand the basic program flow

Dev Tools Setup

---

• JDK-11 - Done
• Git - Done
• Spring Tools - Done
• VS Code - Done
• Node JS - Done
• Postman - Done
• MySQL - Done

Data Types in Java

---

Primary Types:

• Numeric - int - short - byte - long

• Decimal - float - double

• Character- char

• Boolean - boolean (true/false)

• What is the difference between float and double?

Secondary/Referrence Types :

• class

• object

• arrays

• String

• What is typecasting?

• Where do we need it?

How to read input from user

• Import Scanner from util package

import java.util.Scanner;

• Create an object of Scanner

Scanner scan = new Scanner(System.in);

• To read integer :

int num1 = scan.nextInt();

• To read float :

float num1 = scan.nextFloat();

• To read double :

float num1 = scan.nextDouble();

• To read String :

String name = scan.nextLine();

Day 2 Retrospective

---

What did we learn today?

---

• SDLC
• Waterfall vs Agile
• Algorithms and Flowchart
• Java variables and data-type
• typecasting
• How to read input from the user

What did we like?

• we are able to write code
• we are able to run code

Any challenges?

---

What is there for tomorrow?

---

• GIT
• Cotrol flow/ decission making in Java

Day 3 Standup

---

What did we complete yesterday?

What are we going to do today?

GIT and GitLab

• What is git?

• Version Control System

• What is GitLab?

• Online source code repository (remote repository)

• Git has repositories

• We can save our changes to the repository using git commit

• we can push the code to repote repository using git push

• we can clone/make a copy of the remote repository on out local system using git clone

• we can pull the changes from remote repository using git pull

Few GitLab alternatives

• GitHub
• BitBucket
• AWS CodeCommit

What is forking?

Making your own copy of a remote repository

Setting up the SSH key access

Profile -> Preferences -> SSH Keys

• Open Terminal/CMD

• Type bash ssh-keygen -t rsa -b 2048 -C "<email>"

• Enter file in which to save the key

• Enter passphrase

• keep it blank

• Enter same passphrase again

• keep it blank

• Go to the location where keys are saved
• Open the .pub key file using notepad
• Copy the content
• Paste it to the Key section on GitLab
• Add the key
• Also add the private key on your local machine using terminal

eval $(ssh-agent -s)
ssh-add <key-file-name>

How to clone a repository?

1. Go to the repository
2. Click on Clone
3. Clone SSH (_ Copy the link_)
4. Open Termainal/CMD inside your desired folder

• Few important points
• copy the private-key in the desired folder
• Also add the private key on your on that desired folder using terminal/git-bash
• Hints - repeat the eval and ssh-add commands

1. Type git clone <repo-link>

How commit new changes?

1. Add all the changes to stagging git add .
2. Commit the changes git commit -m "a suitable message"

• NB: Commit will save all the changes to local repository

1. Update/Push the commit to remote git push

NB: To see the status of the repository we can use git status

How to get all the changes from remote to local?

git pull

Steps for completing the Exercises/Assignments

1. Go to the respective exercise/assignment repo
2. Fork the repo
3. Clone the forked repo on your local machine (Hints - Follow the previous steps)

• NB. Don't clone a repository inside another repository

1. Modify/Complete the exercise
2. Commit and Push

Conditional evaluation in Java

• if-else
• switch
• conditional operator

How to use if-else in java?

if(condition){
	statements
	...
}
else{
	statements
	...
}

Exercise8: Write an algorithm for accepting a character and then display whether it is a vowel or a constant.

Solution : https://gitlab-ust.stackroute.in/ramanujds9/ust-b2-classroom-repo/-/blob/master/java-basics/Exercise8.java

Exercise 9: Write an algorithm for accepting three numbers and display the highest number among the three numbers.

Solution: https://gitlab-ust.stackroute.in/ramanujds9/ust-b2-classroom-repo/-/blob/master/java-basics/Exercise9.java

Exercise 10: Write an algorithm for accepting the age of user and if the age is valid, check whether the user is a kid, a teenager, an adult or a senior citizen.

Solution : https://gitlab-ust.stackroute.in/ramanujds9/ust-b2-classroom-repo/-/blob/master/java-basics/Exercise10.java

Operators in Java

• Arithmetic Operator

• • • / %

• Relational Operator

< <= > >= == !=

• Logical Operator
• && - AND
• || - OR
• ! - NOT
• Bitwise Operator
• & - Bitwise AND
• | - Bitwise OR
• Assignment Operator
• =
• Arithmetic Assignment Operator
• += -= *= /= %=
• Increment/Decrement Operator
• ++ --

FizzBuzz Program

• Read an input
• if number is divisible by 3 Print Fizz
• if number is divisible by 5 Print Buzz
• if number is divisible by both 3 & 5 Print FizzBuzz
• otherwise print the number

Sample Output

• Input : 6
• Output : Fizz
• Input : 15
• Output : FizzBuzz
• Input : 4
• Output : 4

Day 3 Retrospective

What did we learn today?

• Git:

• How to setup git for clone, commit and push

• Creating ssh keys

• How to complete exercises on stackroute platform?

• Java :

• Conditional evaluation in Java

• if else

• switch

• conditional operator statement

• Different Operators in java

• Completed multiple programs

What went well?

• Able to write code and execute
• Able to understand the concepts

Any challenges?

• gitlab is not accessible through UST Networks

What are we going to learn tomorrow?

• switch
• conditional operator statement
• Looping

Day 4

What did we complete yesterday?

if-else

What are we going to learn today?

switch conditional operator looping

---

switch statement :

Syntax

switch(variable){
	case value1:
		statement;
		break;
	case value2:
		statement;
		break;
	...
	...
	default:
		statement;
		break;
}

Conditional operator statement

Syntax

output = expression ? value if true : value if false

	int num1, num2;
	num1 = 20;
	num2 = 10;
	int largest = num1>num2 ? num1 : num2;
	System.out.println(largest);

Display message based on the day.

int day;

day = 1 message = "Monday - its time to start the week" day = 2 message = "Tuesday - ...." .. .. day = 6 message = "Saturday - Enjoy your weekend" day = 7 message = "Sunday - Plan for the upcoming week"

Looping

while do-while for

Print the message "Welcome to UST Global" 5 times

while(condition){ statement; ... }

do-while loop :

do{ statements; .... }while(condition)

while - entry-controlled do-while - exit-controlled

for loop

for(initialization ; condition ; increment/decrement){ statements; ... }

for(int count=10 ; count<5 ; count++){ System.out.println("Welcome to UST Global"); }

Day 4 Retrospective

What did we learn today?

• Conditional evaluation with switch statement
• using ternary/conditional operator
• loops
• understand the need for loops
• explored different types of loops
• the use of break and continue
• 10+ Problems related to looping and conditional statements are Done

What went well?

• Shoutout to Alphons for completing the tasks quickly
• Shoutout to Shafna for completing the tasks quickly
• Shoutout to Amal for completing the tasks quickly

Any challenges?

• No issues

What is there for tomorrow?

• arrays
• String

---

Day 5:

Arrays

• collection of values

• How to define an array?

data-type []array-name = new data-type[size];

int []numbers; numbers = new int[5];

• new keyword is used for dynamic allocation

int x = 5;

int []data = {10,15,20,30};

data.length; returns the length of the array

Printing an array :

for(int index=0; index<nums.length; index++)
			System.out.println(nums[index]);

How to work with Multi-Dimensional Array

---

2D Array -> Matrix

int [][]matrix = new int[3][3];

Strings in Java

String str = "karan"; String str2 = "rohit"; String str3 = "Rohit"; String email = "rohit12@yahoo.com";

• How to check the equality of two strings :

str.equals(str2) -> false str2.equals(str3) -> false str2.equalsIgnoreCase(str3) -> true

• How to compare two Strings? String str1 = "karan abc"; String str2 = "karan"; int difference = str1.compareTo(str2);

• How to get the length of a string?

  str1.length();

• How to get the character at a position? str1.charAt(3) -> a

• How to get the position of a character?

  str1.indexOf("n") -> 4 str1.indexOf("a") -> 1

• How to check whether a string contains another string?

  String line = "hello karan, how are you doing?"

  line.contains("karan") -> true

  line.indexOf("rahul") -> -1

Complete the first four challenges -- https://www.hackerrank.com/domains/java

Practice Statement - Unique Arrays

A company has revamped the health insurance policy for all its insured employees and has increased their health cover by 20%. In order to provide them this facility, the human resource department needs to collect the data of all insured employees and prepare a unique list of their employee ids.​ Write a program to help the HR manager to create a unique list of employee ids to avoid duplication.​​

Example

Sample Input :
    int[] salesDepartmentEmpIds = {101,105,106,107,108,109};
Sample Output:
    true
---------------------------------------------
Sample Input :
    int[] accountDepartmentEmpIds = {201,205,206,207,208,209,201};
Sample Output:
    false

Practice Statement - Shortest word

Write a Java program to get the strings as input from the user and push them to an array. Find the shortest word in the list of strings and display the same on the screen.

Sample Input

words[] = {"Atrocity", "Pensive", "Imperceptible", "Discordant" }

Sample Output

Shortest word is Pensive

StringBuilder and StringBuffer

Strings cannot be modified StringBuffer and StringBuilder are mutable

How to create StringBuilder?

StringBuilder sbd = new StringBuilder("hello"); StringBuffer sbr = new StringBuffer("welcome");

• StringBuffer vs StringBuilder StringBuffer is Thread-Safe StringBuilder methods are asynchronous

• Reversing a given String

• replace an word with another word String str = "hello everyone, how are you? Everyone should complete the task" Replace everyone with folks

str=str.replace("everyone","folks");

str.split(" ") -> will create an array of strings containing all the words in str separated by space

str.split(",") -> will create an array of strings containing all the words in str separated by comma

trim() -> removes all the trailing spaces

What are we going to learn today?

classes methods objects

find the minimum of two numbers

int findMin(int num1, int num2){

}

find the average of 3 numbers

double findAverage(int num1, int num2, int num3){

}

• Print string in uppercase

  void printString(String str){ System.out.println(str.toUpperCase()); }

-- Sort an array

static int[] sort(int []arr){ ... }

---

method - > self contained block of statement

return-type method-name(arguments)

class - data(fields) + methods

class is a user-defined type

class Employee{
	int employeeId;
	String employeeName;
	String email;

	public printEmployee(){
		System.out.println("ID : "+	employeeId);
		System.out.println("Name : "+employeeName);
		System.out.println("Email : "+email);
	}
}
	

Employee e1 = new Employee();
Employee e2 = new Employee();

What is a Constructor?

• is a special type of method is used for initializing the fields

• it has the same name as the class

• it invokes automatically when we create an object

Day 6 Retrospective

---

What did we learn today?

• String vs StringBuffer/StringBuilder
• Using methods in Java.
• What is a class in java
• What are objects.
• How to create objects in Java
• Significance of static keyword in java

What went well?

• We have gone through multiple examples to understand the concept of classes and objects

Any challenges?

• New concepts.. Need more practice and hands-ons

What is there for tomorrow?

• understand the use of this keyword
• explore different features of OOP
• Understand encapsulation
• Access modifiers

Access Modifiers in Java

• public
• private
• protected
• default

Practice : Inheritance

1. Implement an abstract superclass called Item and define all common operations on this class (constructors, getters, setters, equals, toString, print, checkIn, checkOut, addItem, etc). Have private data for: identification number, title, and number of copies.
2. Implement an abstract subclass of Item named WrittenItem and define all common operations on this class. Added private data for author.
3. Implement 2 subclasses of WrittenItem: Book and JournalPaper.
   3.1. Class Book: no new private data. When needed, override/overload methods from the superclass. 3.2. Class JournalPaper: added private data for year published. When needed, override/overload methods from the superclass.
4. Implement another abstract subclass of Item named MediaItem and define all common operations on this class. Added private data for runtime (integer).
5. Implement 2 subclasses of MediaItem: Video and CD.
   5.1. Class Video: added private data for director, genre and year released. When needed, override/overload methods from the superclass. 5.2. Class CD: added private data for artist and genre. When needed, override/overload methods from the superclass.
   Write the definitions of these classes and a client program (your choice!) showing them in use.

Day 11 Retrospective

What did we learn today?

• Inheritance
• Method overriding
• use of super keyword
• use of protected access modifier

What went well?

• Able to write code related to inheritance

What needs to be improved?

• More practice on logical problem solving

What is there for tomorrow?

• abstract classes
• interfaces
• final keyword

Any task for tomorrow?

• Complete all the problems mentioned on additional-exercises of GitLab.

• explore instance of operator

final keyword in java

• final variables are treated as constants and the value of the variable cannot be changed

• final methods cannot be overridden

• final class cannot be inherited

Abstraction in Java

Abstraction can be achieved in two ways -

1. Using abstract classes
2. Using interfaces

Has A

class Phone{ Sim sim; makeACall(){ sim.call(); }

}

class Sim{ call(){ ... } sendSms(){ ... }

Printer

Some Printers are Scanner too

HpPrinter - can only print CanonPrinter - can print and scan

We need a printer object which can be initialised with either of the different printer available

Exception Handling

try - write the code that can lead to some exception

catch - write what to be done if the exception occurred

finally - a code block to be executed irrespective of whether or not the exception occurred

Exception are of two types -

Checked Exception - Compile-Time exception Unchecked Exception - Runtime Exception

ArrayIndexOutOfBoundsException

All checked exception extends the Exception class directly examples - FileNotFoundException, SQLException, IOException, ClassNotFoundException

All unchecked exception extends the RuntimeException class examples - ArithmeticException,ArrayIndexOutOfBoundsException, NullPointerException, InputMismatchException, NumberFormatException

How to catch more than one exceptions?

How to throw and exception conditionally?

Throw vs Throws

• with throw we can generate an exception

• syntax : throw new Exception-class-name(message)

• example : throw new InvalidAgeException("Invalid Age")

• with throws we declare an exception (checked-exception)

• syntax : method-name() throws Exception-Type

• example : public void readAge() throws InvalidAgeException

Collection Framework

• provides a set interfaces and classes

• 3 types

• List - collection(index based, allows duplicates)

  • ArrayList
  • LinkedList
  • Vector

• Queue

  • First-In-First-Out Data Structure
  • Allows duplicates
    • PriorityQueue
    • LinkedList

• Set

  • collection of unique elements(hash based)
  • HashSet
  • TreeSet

Generic Types

- Generic types defines the type of data that a collection should have
- we mention generic types using <> diamond braces  

How to sort a collection?

Collections.sort(list)

How to sort a List of Customer?

• implement the Comparable interface

• override the compareTo() method

Example :

class Customer implements Comparable<Customer>{
	
	....
	
	public int compareTo(Customer c) {
		
		....
	}	
	
}

• create an exception DuplicateCustomerException and throw it when you try to add the customer with same id

Map

• consists of key value pair
• Keys are unique

	Map<K,V> map = new HashMap<>()

	Map<Integer, String> myMap = new HashMap<>()

Layered Architecture

• we divide different classes an interfaces as per their purpose

• ui layer

• business layer / service layer

• repository layer/DAO Layer/Persistence Layer

• model/entity layer

Software Testing

• Unit Testing

• Integration Testing

• End-to-End Testing

• JUnit - Java Library for writing unit tests

• Lifecycle hooks

• BeforeAll

• BeforeEach

• AfterEach

• AfterAll

Reading a file

• FileInputStream - Byte Oriented
• FileReader - Character Oriented

Writing objects to file

Serialization

Reading object from file

De-serialization

Database Management System

ER Model Entity Relationship Diagram

Entity - is an object of interest Attribute - Defines various properties of an entity Relationship - Defines the relationship between different entities

Trainee

Trainer

--Employee Table--

emp_id	emp_name	email	job	salary	hiredate
1001	Suraj	suraj@yahoo.com	Clerk	65000	2020-04-27
1002	Mohit	mohit@gmail.com	Salesman	52000	2021-04-20
1003	Gaurav	gaurav@yahoo.com	Analyst	55000	2020-10-15
1004	Harsh	harsh@gmail.com	Clerk	68000	2019-02-10
1005	Javed	javed@yahoo.com	Manager	85000	2015-05-20
2001	Priyanka	priyanka@yahoo.com	Analyst	75000	2018-05-20
2002	Karan	karan@yahoo.com	Analyst	72000	2019-10-20

Types of SQL Commands

• DDL

  • CREATE : creating new table or database
  • ALTER : changing the table structure
  • DROP : delete the table
  • TRUNCATE : clear all the data

• DML

  • INSERT
  • UPDATE
  • DELETE

• DQL

  • SELECT

Code Quality Check

SonarQube Download From

Version compatible with JDK 11 :

https://binaries.sonarsource.com/Distribution/sonarqube/sonarqube-8.9.10.61524.zip

Steps :

1. Download SonarQube

2. Extract and Run StartSonar.bat

3. Visit localhost:9000 and change the security settings

4. Make the following changes

Maven Configuration

• Add the following dependencies and plugins to your maven project

pom.xml

	<properties>
		<maven.compiler.source>11</maven.compiler.source>
		<maven.compiler.target>11</maven.compiler.target>

		<!-- JaCoCo Properties -->
		<jacoco.version>0.8.6</jacoco.version>
		<sonar.java.coveragePlugin>jacoco</sonar.java.coveragePlugin>
		<sonar.dynamicAnalysis>reuseReports</sonar.dynamicAnalysis>
		<sonar.coverage.jacoco.xmlReportPaths>${project.basedir}/../target/jacoco.exec</sonar.coverage.jacoco.xmlReportPaths>
		<sonar.language>java</sonar.language>

	</properties>


	<dependencies>

		<dependency>
			<groupId>org.jacoco</groupId>
			<artifactId>jacoco-maven-plugin</artifactId>
			<version>0.8.6</version>
		</dependency>

		<!-- https://mvnrepository.com/artifact/org.sonarsource.scanner.maven/sonar-maven-plugin -->
		<dependency>
			<groupId>org.sonarsource.scanner.maven</groupId>
			<artifactId>sonar-maven-plugin</artifactId>
			<version>3.9.1.2184</version>
		</dependency>



		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-api</artifactId>
			<version>5.8.2</version>
			<scope>test</scope>
		</dependency>

		<dependency>
			<groupId>org.junit.jupiter</groupId>
			<artifactId>junit-jupiter-engine</artifactId>
			<version>5.8.2</version>
			<scope>test</scope>
		</dependency>




	</dependencies>

	<build>
		<plugins>
			<plugin>
				<groupId>org.jacoco</groupId>
				<artifactId>jacoco-maven-plugin</artifactId>
				<version>${jacoco.version}</version>
				<executions>
					<execution>
						<id>jacoco-initialize</id>
						<goals>
							<goal>prepare-agent</goal>
						</goals>
					</execution>
					<execution>
						<id>jacoco-site</id>
						<phase>package</phase>
						<goals>
							<goal>report</goal>
						</goals>
					</execution>
				</executions>
			</plugin>
			<plugin>
				<groupId>org.jacoco</groupId>
				<artifactId>jacoco-maven-plugin</artifactId>
				<executions>
					<execution>
						<id>report</id>
						<goals>
							<goal>report-aggregate</goal>
						</goals>
						<phase>verify</phase>
					</execution>
				</executions>
			</plugin>

			<plugin>
				<artifactId>maven-surefire-plugin</artifactId>
				<version>2.19</version>
				<dependencies>
					<dependency>
						<groupId>org.junit.platform</groupId>
						<artifactId>junit-platform-surefire-provider</artifactId>
						<version>1.0.0</version>
					</dependency>
				</dependencies>
			</plugin>
		</plugins>
	</build>

Run your project as Maven Build with goal

clean verify sonar:sonar

Visit localhost:9000

Regular Expression

---

Examples - [abc] -> either a or b or c str = "a"

[abc]* -> zero or more numbers of a or b or c str = "abaac";

[abc]+ -> one or more numbers of a or b or c

[a-z]* -> zero or more character

[a-zA-Z]* -> zero or more character including uppercase

[a-zA-Z0-9]* -> zero or more character including digits

[0-9]{10} -> a 10 digit number

[0-9]{8,10} -> a digit with 8 to 10 numbers

[0-9]{,10} -> max 10

[0-9]{10,} -> min 10

\w == [a-zA-Z0-9]

\d == [0-9]

\s == white-space

\W == non character

\D == non-digit

\S == no space

Password Validation Given a method with a password in string format as input. Write code to validate the password using following rules:

• Must contain at least one digit
• Must contain at least one of the following special characters @, #, $
• Length should be between 6 to 20 characters.

String password -> "^(?=.*\\d)(?=.*[@#$])[a-zA-Z0-9@#$]{6,20}$";

Explanation:

^ - the start of the string

(?=.*\d) -> positive lookahead that checks if the string contains at least one digit

(?=.*[@#$]) -> positive lookahead that checks if the string contains at least one of the special characters @, #, or $

[a-zA-Z0-9@#$]{6,20} -> matches any combination of upper or lowercase letters, digits, and the special characters @, #, and $, with a length between 6 and 20 characters

$ -> the end of the string

UML Important points

Class Diagram

Decomposition

Association

Where both the object can exists individually

• Flight and Passengers
• Fridge and Fruits

Aggregation

It a Has-A relationship where one object is dependent on the other

• Flight and Crew-Member

Composition

It is a strong Has-a relationship where both objects are dependent on each other and no one can exists individually

• Person and Brain
• Car and Engine
• Employee and Salary

Generalisation

Inheritance

Animal

• • color
• • size
• • speak()

Cat extends Animal

• speak(){

}

Dog extends Animal

• speak(){ Sysout("Bark..") }

SOLID Principle

https://www.freecodecamp.org/news/solid-principles-explained-in-plain-english/

SOLID Principle

Single Responsibility Principle

The Single Responsibility Principle states that a class should do one thing and therefore it should have only a single reason to change.

For example in our Customer-Management-App we divided our classes into multiple layers and every class has a single responsibility, eg. CustomerRepository class does Database related task only and CustomerService class does service and business related task only.

Open-Closed Principle

Open-Closed Principle requires that classes should be open for extension and closed to modification.

Eg. currently we are storing the customers to HashMap, if we want to change our storage to a database then we should not modify the existing Class rather we should extend a new class and write code to database operation.

Liskov Substitution Principle

Liskov Substitution Principle states that subclasses should be substitutable for their base classes.

for example the sort method in Collections class requires a List and it can be substituted by ArrayList, LinkedList or any other subclasses of List.

Collections.sort(List items)

Interface Segregation Principle

Segregation means keeping things separated, and the Interface Segregation Principle is about separating the interfaces.

interface Printer{
 void print();
}

interface Scanner{
 void scan();
}

class HPPrinter implements Printer,Scanner{
	public void print(){
	
	}
	public void scan(){
	
	}
}

class CanonPrinter implements Printer{
	public void print(){
	
	}
	
}

Dependency Inversion Principle

The Dependency Inversion principle states that our classes should depend upon interfaces or abstract classes instead of concrete classes and functions.

How to insert a row in a database using JDBC

---

Steps:

1. Add the database driver
2. Create a connection
3. Create a statement
4. Execute statement
5. Display output

HTML Basics

HTML Tags(elements) are of two types

• container tag -- contains both opening and closing tags -- h1,p,html,body
• empty tag -- no closing -- br,hr,img,input

Some important tags

• - paragraph
• - division

• h1 to h6 are headings

• ---

  - horizontal line

• 
  - line break

• HTML Lists

---

Two types

• unordered list

• ordered list

• description list

• HTML Tables

• HTML text formatting

• HTML links

• Inline and Block elements -- Block - div, p, h1,..,h6 -- Inline - span, img, input

HTML Forms

CSS

How to use css?

{property:value;}

Inline CSS Internal CSS External CSS

CSS Displays

HTML 5 new Tags

Bootstrap

JavaScript

How to include JS in your html?

• Inline JS
• Internal JS
• External JS

JavaScript variables and Data types

number - 5, 2.5, -3.65546 string - 'hello', "rahul", """harsh""",javed boolean - true/false object -

let employee1 = { employeeId : 1001, employeeName: 'Rahul' }

let employee2 = { employeeId : 1002, email: 'gaurav@yahoo.com' }

Date - represents a date

How to declare variables

x = 10 // global declaration var y = 20 // function level declaration let z = 30 // block level declaration

JavaScript basic building blocks

Control-Statements

• if-else
• switch
• conditional operator(?:)

Looping

while do-while for

Equals in JavaScript

= - assignment == - compares values irrespective of type === - compares values and type

Arrays

let arr = [10,20,30,'Ramesh','Suresh'];

REST APIs using AJAX

npm set strict-ssl false
npm install g json-server
json-server employees.json --port=3500

GET :

localhost:3500/employees

localhost:3500/employees?name=Harsh

localhost:3500/employees/1001

POST :

localhost:3500/employees

Body : { "id":1005, "name":"Suraj", "email":"suraj@yahoo.com" }

DELETE:

localhost:3500/employees/1002

PUT:

localhost:3500/employees/1005

Body : { "id":1005, "name":"Suraj Sharma", "email":"suraj@yahoo.com" }

POST Request

fetch('https://jsonplaceholder.typicode.com/todos', {
        method: 'POST',
        body: JSON.stringify(todo),
        headers: {
            'Content-type': 'application/json; charset=UTF-8'
        }
    })

J2EE Programming

Server :

• Tomcat Server

Servlet:

Java code that runs on server

Spring Framework

Java Framework :

• Spring Core Dependency Injection
• Spring MVC
• Spring Boot
• Spring Security
• Spring Cloud

What is a dependency?

Phone{ Sim sim; .. .. }

Sim{ .... }

Spring Bean

IOC Container

Autowiring

Injecting dependency automaticaly

• By Type
• By Name

DI has 3 Types

Setter Injection Constructor Injection Field Injection

Important Annotations

@Component
@Service
@Repository

@ComponentScan

@Autowired

@Configuraion

@Bean

@Value

@Qualifier

@PropertySource

Spring Boot

• spring project
• production ready standalone spring-based application
• focuses on convention over configuration

How to create a spring boot app?

• create a spring starter project
• select the dependencies you need
• create the project

Swagger UI

localhost:8000/swagger-ui.html

@SpringBootApplication

• declares a SpringBootApplication and do all the necessary configuration

@RestController

• creates a REST API(returns resources[json])

@Controller

• creates a Controller that returns a view(a page)

@RequetBody

• to map the data received from the body of the request to a java object

@ResponseBody

• creates a REST API inside a Controller (returns resources[json])

@RequestMapping

• maps a method to a request(any type of request)

@GetMapping

• maps a method to a GET request

@PostMapping

• maps a method to a POST request

@DeleteMapping

• maps a method to a DELETE request

@PutMapping

• maps a method to a PUT request

@ResponseStatus

• used to change the status code of the response

@PathVariable

• to read dynamic from the URI

@RequestParam

• to read the query parameter from the request