Java provides a number of access modifiers to set access levels for classes, variables, methods, and constructors. The four access levels are − Show
Default Access Modifier - No KeywordDefault 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. ExampleVariables and methods can be declared without any modifiers, as in the following examples − String version = "1.5.1"; boolean processOrder() { return true; }Private Access Modifier - PrivateMethods, 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. ExampleThe following class uses private access control − public class Logger { private String format; public String getFormat() { return this.format; } public void setFormat(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. Public Access Modifier - PublicA 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. ExampleThe following function uses public access control − public static void main(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. Protected Access Modifier - ProtectedVariables, 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. ExampleThe following parent class uses protected access control, to allow its child class override openSpeaker() method − class AudioPlayer { protected boolean openSpeaker(Speaker sp) { // implementation details } } class StreamingAudioPlayer extends AudioPlayer { boolean openSpeaker(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. Access Control and InheritanceThe following rules for inherited methods are enforced −
java_modifier_types.htm ModifiersBy now, you are quite familiar with the public keyword that appears in almost all of our examples: The public keyword is an access modifier, meaning that it is used to set the access level for classes, attributes, methods and constructors. We divide modifiers into two groups:
Access ModifiersFor classes, you can use either public or default:
For attributes, methods and constructors, you can use the one of the following:
Non-Access ModifiersFor classes, you can use either final or abstract:
For attributes and methods, you can use the one of the following:
FinalIf you don't want the ability to override existing attribute values, declare attributes as final: Examplepublic class Main { final int x = 10; final double PI = 3.14; public static void main(String[] args) { Main myObj = new Main(); myObj.x = 50; // will generate an error: cannot assign a value to a final variable myObj.PI = 25; // will generate an error: cannot assign a value to a final variable System.out.println(myObj.x); } }Try it Yourself » StaticA static method means that it can be accessed without creating an object of the class, unlike public: ExampleAn example to demonstrate the differences between static and public methods: public class Main { // Static method static void myStaticMethod() { System.out.println("Static methods can be called without creating objects"); } // Public method public void myPublicMethod() { System.out.println("Public methods must be called by creating objects"); } // Main method public static void main(String[ ] args) { myStaticMethod(); // Call the static method // myPublicMethod(); This would output an error Main myObj = new Main(); // Create an object of Main myObj.myPublicMethod(); // Call the public method } }Try it Yourself » AbstractAn abstract method belongs to an abstract class, and it does not have a body. The body is provided by the subclass: Example// Code from filename: Main.java // abstract classabstract class Main { public String fname = "John"; public int age = 24; public abstract void study(); // abstract method } // Subclass (inherit from Main) class Student extends Main { public int graduationYear = 2018; public void study() { // the body of the abstract method is provided here System.out.println("Studying all day long"); } } // End code from filename: Main.java // Code from filename: Second.java class Second { public static void main(String[] args) { // create an object of the Student class (which inherits attributes and methods from Main) Student myObj = new Student(); System.out.println("Name: " + myObj.fname); System.out.println("Age: " + myObj.age); System.out.println("Graduation Year: " + myObj.graduationYear); myObj.study(); // call abstract method } } Try it Yourself » Which access modifier makes the code accessible within the same class?Access Modifiers. Which access modifier can be accessed within a class?For members, there are two additional access modifiers: private and protected . The private modifier specifies that the member can only be accessed in its own class.
What are the 3 access modifiers?C++ uses the three modifiers called public , protected , and private .
Which access specifier method can be accessible in same class and only inside the package?Default: When no access modifier is specified for a class, method, or data member – It is said to be having the default access modifier by default. The data members, class or methods which are not declared using any access modifiers i.e. having default access modifier are accessible only within the same package.
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