the practice of hiding the internal details of an object and exposing only the necessary information to the outside world.

the ability of objects to take on multiple forms.

the practice of defining objects at a higher level based on their behavior and hiding the implementation details

Public

Package

Protected

Private

Both XXXXX and ppp will be displayed once

Prints ppp 8 times and XXXXX 7 times

Prints XXXXX 15 times

Prints ppp 15 times

Prints XXXXX 8 times and ppp 7 times

Complete

Cimpletd

Coipletd

Iomplede

Writing code

Compilation error

Writing… 

Writing code

Writing book

2 and 2

1 and 3

2 and 1

1 and 2

error

A file can contain only one public class

A file can have a name different from the name of the public class defined in it.

It is possible to declare several public classes in the same file.