In Java, what is the difference between default, public, protected, and private?

Question

What are all the access specifiers and their restrictions in Java?
What are the rules on when to use which access specifier?

Answer 1

As per the official tutorial below is the sorted list of access modifiers in which we accessibility increases from left to right..

private < default < protected < public

Table of access of different access modifiers at different levels-

            | Class | Package | Subclass | Subclass | World
            |       |         |(same pkg)|(diff pkg)| 
————————————+———————+—————————+——————————+——————————+————————
public      |   *   |    *    |    *     |     *    |   *     
————————————+———————+—————————+——————————+——————————+————————
protected   |   *   |    *    |    *     |     *    |         
————————————+———————+—————————+——————————+——————————+————————
no modifier |   *   |    *    |    *     |          |    
————————————+———————+—————————+——————————+——————————+————————
private     |   *   |         |          |          |    

* : accessible
blank : not accessible