base64 encode

import java.util.Base64;

class Main {

  public static void main(String[] args) {

  // Encode

String originalInput = "test input";

String encodedString = Base64.getEncoder().encodeToString(originalInput.getBytes());

System.out.println(encodedString); // Output will be: c29tZSBzdHJpbmc=

// Decode

byte[] decodedBytes = Base64.getDecoder().decode(encodedString);

String decodedString = new String(decodedBytes);

System.out.println(decodedString);

  }

}

springboot application configuration

https://o7planning.org/en/11267/spring-boot-tutorial-for-beginners

https://reflectoring.io/bean-validation-with-spring-boot/

aws cognito

https://medium.com/@prasadjay/amazon-cognito-user-pools-in-nodejs-as-fast-as-possible-22d586c5c8ec

socket tutorial link

https://socket.io/get-started/chat/

url naming convention

https://restfulapi.net/resource-naming/

get email first part in java

class Main {

  public static void main(String[] args) {

    String email="pawan@gmail.com";

    Integer index=email.indexOf('@');

    String name=email.substring(0,index);

    System.out.println("Hello world!"+name);

  }

}

Valid email defination

https://help.returnpath.com/hc/en-us/articles/220560587-What-are-the-rules-for-email-address-syntax-

For an email to be delivered, it must have a valid address that follows certain rules of syntax.

A valid email address has four parts:

• Recipient name
• @ symbol
• Domain name
• Top-level domain

Recipient name
The recipient name represents an email mailbox that belongs to:

• A specific person
• A mailing list
• A department
• A role within a company (such as sales or customer service)

The recipient name may be a maximum of 64 characters long and consist of:

• Uppercase and lowercase letters in English (A-Z, a-z)
• Digits from 0 to 9
• Special characters such as ! # $ % & ' * + - / = ? ^ _ ` { |

email id validation with cutom special char

^[ A-Za-z0-9_@./'*#&+-]*$

import java.util.regex.Matcher;

import java.util.regex.Pattern;

class Main {

  public static void main(String[] args) { 

    System.out.println("Hello world!");

    String email="pawan*k@ed-ynamic.com";

    String regex = "^[ A-Za-z0-9_@./'*#&+-]*$";

    Pattern pattern = Pattern.compile(regex);

    Matcher matcher = pattern.matcher(email);

    System.out.println("--opp---"+ matcher.matches());

    //return matcher.matches();

  }

}

"^[_A-Za-z0-9-\\+_@./'*#&+-]+(\\.[_A-Za-z0-9-_@./'*#&+-]+)*@" + "[A-Za-z0-9-_@./'*#&+-]+(\\.[A-Za-z0-9_@./'*#&+-]+)*(\\.[A-Za-z_@./'*#&+-]{2,})$"
; https://stackoverflow.com/questions/17439917/regex-to-accept-alphanumeric-and-some-special-character-in-javascript https://www.computerhope.com/unix/regex-quickref.htm start and end with alpha numeric

class Main {

  public static void main(String[] args) { 

    System.out.println("Hello world!");

    String email="a-alsaqal@mada.jo.com.in";

    String regex ="^[a-zA-Z0-9_.+-]+@[a-zA-Z0-9-]+\\.[a-zA-Z0-9-.]+[a-zA-Z0-9]$";

    Pattern pattern = Pattern.compile(regex);

    Matcher matcher = pattern.matcher(email);

    System.out.println("--opp---"+ matcher.matches());

    //return matcher.matches();

  }

}

Valid Email ID

https://help.returnpath.com/hc/en-us/articles/220560587-What-are-the-rules-for-email-address-syntax-

regular expression tutorial

https://medium.com/factory-mind/regex-tutorial-a-simple-cheatsheet-by-examples-649dc1c3f285

email validation java

import java.util.regex.Matcher;

import java.util.regex.Pattern;

class Main {

  public static void main(String[] args) {

    System.out.println("Hello world!");

    String email="pawan,k@gmail.com";

        String regex ="^[_A-Za-z0-9-\\+]+(\\.[_A-Za-z0-9-]+)*@" + "[A-Za-z0-9-]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$";

    Pattern pattern = Pattern.compile(regex);

    Matcher matcher = pattern.matcher(email);

    System.out.println("--opp---"+ matcher.matches());

    //status= matcher.matches();

     //System.out.println("Hello world!"+status);

  }

}

JDBC Difference between execute, executeQuery and executeUpdate in JDBC

https://www.javapedia.net/JDBC/1793

execute method can be used with any type of SQL statements and it returns a boolean. A true indicates that the execute method returned a result set object which can be retrieved using getResultSet method. false indicates that the query returned an int value or void. execute method can run both select and insert/update statements.

executeQuery method execute statements that returns a result set by fetching some data from the database. It executes only select statements.

executeUpdate method execute sql statements that insert/update/delete data at the database. This method return int value representing number of records affected; Returns 0 if the query returns nothing. The method accepts only non-select statements.