Installing MySQL On Ubuntu

Installing MYSQL On Ubuntu

First, update the apt package index by typing:

sudo apt update

Then install the MySQL package with the following command:

sudo apt install mysql-server

Once the installation is completed, the MySQL service will start automatically. To check whether the MySQL server is running, type:

sudo systemctl status mysql

MySQL server package comes with a script called mysql_secure_installation that can perform several security-related operations.

Run the script by typing:

sudo mysql_secure_installation

If you want to login to your MySQL server as root from an external program such as Mysql Workbench you have two options.

The first one is to change the authentication method from auth_socket to mysql_native_password. You can do that by running the following command:

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'very_strong_password';FLUSH PRIVILEGES;

Copy

The second, recommended option is to create a new administrative user with access to all databases:

GRANT ALL PRIVILEGES ON *.* TO 'administrator'@'localhost' IDENTIFIED BY 'very_strong_password';

References:
https://linuxize.com/post/how-to-install-mysql-on-ubuntu-18-04/
https://www.youtube.com/watch?v=ug0TFsort24

Members Access Modifiers

Members Access Modifiers

    Because method and variable members are usually given access control in exactly the same way, we'll cover both together.

Whereas a class can use just two of the four access control levels (default or public ), members can use all four:

- public

- protected

- default

- private

Public Members

    When a method or variable member is declared public, it means all other classes, regardless of the package they belong to, can access the member (assuming the class itself is visible).

example:

public void methodA() { }
public int year;

Private Members

    Members marked private can't be accessed by code in any class other than the class in which the private member was declared.
A method marked private cannot be overridden.

example:

private void methodB() {}
private String name;

Protected and Default Members

    The protected and default access control levels are almost identical, but with one critical difference. A default member may be accessed only if the class accessing the member belongs to the same package, whereas a protected member can be accessed (through inheritance) by a subclass even if the subclass is in a different package.

Note: Default members can be accessed only from the same package and cannot be through inheritance.

example:

abstract class Car {

double price // Default member;

protected void goFast(); // Protected method

void getModel(){}; // Default method

}

Class Access Modifiers

Class Access Modifiers

What does it mean to access a class? When we say code from one class (class A) has access to another class (class B), it means class A can do one of three things:

1- Create an instance of class B.

2- Extend class B (in other words, become a subclass of class B).

3- Access certain methods and variables within class B, depending on the access control of those methods and variables.

Default Access

    Default access It's the access control you get when you don't type a modifier in the class declaration. Think of default access as package-level access, because a class with default access can be seen only by classes within the same package.

example:

class Beverage { }

Public Access

    A class declaration with the public keyword gives all classes from all packages access to the public class. In other words, all classes in the Java Universe (JU) have access to a public class.

example:

public class Beverage { }

Final Class

    When used in a class declaration, the final keyword means the class can't be subclassed. In other words, no other class can ever extend (inherit from) a final class, and any attempts to do so will result in a compiler error.

example:

public final class Beverage {}

Abstract Classes

    An abstract class can never be instantiated. It's sole purpose, mission in life, is to be extended (subclassed). If even a single method is abstract, the whole class must be declared abstract. One abstract method spoils the whole bunch. You can, however, put nonabstract methods in an abstract class.

example:

abstract class Car {

private double price;

public abstract void goFast(); // Abstract method

public void getModel(){}; // Non abstract method

}

Strictfp Class

    Marking a class as strictfp means that any method code in the class will conform to the IEEE 754 standard rules for floating points. Without that modifier, floating points used in the methods might behave in a platform-dependent way.