Java provides four access modifiers to set access levels for classes, variables, methods and constructors.

The four access modifiers are:

·     Public: Visible to the world (public).

·     Protected: Visible to the package and all subclasses only (protected).

·     Private: Visible to the class only (private).

·     Default: Visible to the package. No modifiers are needed.

Public Access Modifier:

If any class, method, constructor, etc. is declared “public”, then it can be accessed from any other class. Therefore methods, blocks declared inside a public class can be accessed from any class belonging to the Java Universe. But then to, if the public class we are trying to access is in some other package, then the public class still need to be imported. Because of class inheritance, all public methods and variables of a class can be inherited by its subclasses.

Protected Access Modifier:

If we declare variables, methods and constructors as “protected” in a superclass, then it can be accessed only by the subclasses in other package or any class within the package of the protected members’ class.

It cannot be applied to class and interfaces. Methods, fields can be declared protected, however methods and fields in an interface cannot be declared protected.

Private Access Modifier:

If we declare any methods, variables and constructors private, then they can only be accessed within the declared class. It is the most restrictive access level. Class and interfaces cannot be private. Variables that are declared private can be accessed outside the class if public getter methods are present in the class.

Declaring the variables and methods as “private” is the best way to encapsulate object and hide its data from the outside world.

Default Access Modifier:

If we do not declare any access modifier for a class, variable, method, etc., then it is consider it to be default access modifier. A variable or method declared without any access modifier is available to any other class in the same package.