Java – Access Modifiers

Java Access Modifiers

The access modifiers in Java are used to specify the scope of the variables, data members, methods, classes, or constructors. These help to restrict and secure the access (or, level of access) of the data.

There are four level of access:

Visible to the package, the default. No modifiers are needed.
Visible to the class only (private).
Visible to the world (public).
Visible to the package and all subclasses (protected).

In this tutorial, we will learn about the Java access modifier and their various types along with the examples.

Types of Java Access Modifiers

There are four different types of access modifiers in Java, we have listed them as follows:

Default (No keyword required)
Private
Protected
Public

1. Default Access Modifier

Default access modifier means we do not explicitly declare an access modifier for a class, field, method, etc.

A variable or method declared without any access control modifier is available to any other class in the same package. The fields in an interface are implicitly public static final and the methods in an interface are by default public.

Example: Default Access Modifier

Variables and methods can be declared without any modifiers, as in the following examples −

String version ="1.5.1";booleanprocessOrder(){returntrue;}

2. Private Access Modifier

Methods, variables, and constructors that are declared private can only be accessed within the declared class itself.

Private access modifier 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.

Using the private modifier is the main way that an object encapsulates itself and hides data from the outside world.

Example 1: Private Access Modifier

The following class uses private access control −

publicclassLogger{privateString format;publicStringgetFormat(){returnthis.format;}publicvoidsetFormat(String format){this.format = format;}}

Here, the format variable of the Logger class is private, so there’s no way for other classes to retrieve or set its value directly.

So, to make this variable available to the outside world, we defined two public methods: getFormat(), which returns the value of format, and setFormat(String), which sets its value.

Example 2: Private Access Modifier

In this example, the data members and class methods of the Logger class are private. We are trying to access those class methods in another class Main.

classLogger{privateString format;privateStringgetFormat(){returnthis.format;}privatevoidsetFormat(String format){this.format = format;}}publicclassMain{publicstaticvoidmain(String[] args){// Creating an object Logger log =newLogger();// Setting the value
    log.setFormat("Text");// Getting the valueSystem.out.println(log.getFormat());}}

Output

Main.java:18: error: setFormat(String) has private access in Logger
    log.setFormat("Text");
       ^
Main.java:20: error: getFormat() has private access in Logger
    System.out.println(log.getFormat());
                          ^
2 errors

3. Protected Access Modifier

Variables, methods, and constructors, which are declared protected in a superclass can be accessed only by the subclasses in other package or any class within the package of the protected members’ class.

The protected access modifier cannot be applied to class and interfaces. Methods, fields can be declared protected, however methods and fields in a interface cannot be declared protected.

Protected access gives the subclass a chance to use the helper method or variable, while preventing a nonrelated class from trying to use it.

Example 1: Protected Access Modifier

The following parent class uses protected access control, to allow its child class override openSpeaker() method −

classAudioPlayer{protectedbooleanopenSpeaker(Speaker sp){// implementation details}}classStreamingAudioPlayerextendsAudioPlayer{booleanopenSpeaker(Speaker sp){// implementation details}}

Here, if we define openSpeaker() method as private, then it would not be accessible from any other class other than AudioPlayer. If we define it as public, then it would become accessible to all the outside world. But our intention is to expose this method to its subclass only, that’s why we have used protected modifier.

Example 2: Protected Access Modifier

This example demonstrates the use of protected access modifier.

// Class OneclassOne{protectedvoidprintOne(){System.out.println("printOne method of One class.");}}// Inheriting class One on MainpublicclassMainextendsOne{publicstaticvoidmain(String[] args){// Creating an object of Main classMain obj =newMain();// Calling printOne() method of class One// through the object of Main class
    obj.printOne();}}

Output

printOne method of One class.

4. Public Access Modifier

A class, method, constructor, interface, etc. declared public can be accessed from any other class. Therefore, fields, methods, blocks declared inside a public class can be accessed from any class belonging to the Java Universe.

However, if the public class we are trying to access is in a different package, then the public class still needs to be imported. Because of class inheritance, all public methods and variables of a class are inherited by its subclasses.

Syntax

The following function uses public access control −

publicstaticvoidmain(String[] arguments){// ...}

The main() method of an application has to be public. Otherwise, it could not be called by a Java interpreter (such as java) to run the class.

Example: Public Access Modifier

This example demonstrates the use of public access modifier.

// Class OneclassOne{publicvoidprintOne(){System.out.println("printOne method of One class.");}}publicclassMain{publicstaticvoidmain(String[] args){// Creating an object of class OneOne obj =newOne();// Calling printOne() method of class One
    obj.printOne();}}

Output

This example demonstrates the use of public access modifier.