Objects

Software objects are conceptually similar to real-world objects: they too consist of state and related behavior.
An object stores its state in fields (variables in some programming languages) and exposes its behavior through methods (functions in some programming languages).
Hiding internal state and requiring all interaction to be performed through an object’s methods is known as data encapsulation
Bundling code into individual software objects provides a number of benefits, including:

Modularity: The source code for an object can be written and maintained independently of the source code for other objects
Information-hiding: By interacting only with an object’s methods, the details of its internal implementation remain hidden from the outside world.
Code re-use: If an object already exists (perhaps written by another software developer), you can use that object in your program
Pluggability and debugging ease: If a particular object turns out to be problematic, you can simply remove it from your application and plug in a different object as its replacement

Classes

A class is the blueprint from which individual objects are created.
class does not contain a main method that’s because it’s not a complete application; it’s just the blueprint for bicycles that might be used in an application

Object-oriented programming allows classes to inherit commonly used state and behavior from other classes.
The syntax for creating a subclass is simple. At the beginning of your class declaration, use the extends keyword, followed by the name of the class to inherit from.

Every digit in a decimal number has a “position”, and the decimal point helps us to know which position is which: decimal

Every position further to the left is 10 times bigger, and every position further to the right is 10 times smaller.
decimal number system it also called big10 system, because it based on number 10