Java 17 Recipes

5-1. Controlling Access to Members of a Class
 Problem
You want to create members of a class that are not accessible from any other class.
 Solution
Create private instance members rather than making them available to other classes 
(public or protected). For instance, suppose you are creating an application to manage 
a team of players for a sport. You create a class named Player that represents a player on 
the team. You do not want the fields for that class to be accessible from any other class. 
The following code demonstrates the declaration of some instance members, making 
them accessible only from within the class in which they were defined.
private String firstName;
private String lastName;

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152
private String position;
private int status = -1;
 How It Works
To designate a class member as private, prefix its declaration or signature using the 
private keyword. The private access modifier hides members of a class so that outside 
classes cannot access them. Any members of a class marked as private are available 
only to other members of the same class. Any outside class cannot access fields or 
methods designated as private, and an IDE that uses code completion cannot see them.
As mentioned in the solution to this recipe, three different access modifiers can be 
used when declaring members of a class. Those modifiers are public, protected, and 
private. Members that are declared as public are available for any other class. Those 
declared as protected are available for any other class within the same package and 
subclasses. It is best to declare public or protected only those class members that need 
to be directly accessed from another class. Hiding members of a class using the private 
access modifier helps to enforce better object-orientation. Moreover, a default scope is 
accessible from the package and the class— that occurs when it is not assigned scope to 
a class element.