Access Modifiers in Java is a security mechanism that restricts the accessibility of certain members of a class to specific parts of a program. It is also called as Access Control in Java. This helps to protect the data and code in our program from unauthorized access.
Table of Contents
What is access modifiers?
Access modifiers are keywords that can be used to specify the accessibility of a class member, such as a field, method, or constructor.
Why access modifier is important?
Access Modifiers is important for a number of reasons, including:
- Security: Access modifiers help to protect the data and code in our program from unauthorized access.
- Encapsulation: Access modifiers help to encapsulate the data and code in our program, making it easier to maintain and extend.
- Reusability: Access modifiers make easier to reuse code from other classes, as we can be confident that the code is not accessible to unauthorized classes.
What are the four types of access modifiers in Java?
There are four types of access modifiers in Java:
- Public: Public members are accessible from anywhere in the program.
- Protected: Protected members are accessible from within the same package and from subclasses of the class in which they are declared.
- Default: Default members are accessible from within the same package.
- Private: Private members are only accessible from within the class in which they are declared.
The following table summarizes the access level of these access modifiers.
| Access Level | Description |
|---|---|
| Public | Members are accessible from anywhere in the program. Public access can be given by using the public keyword. |
| Protected | Members are accessible from within the same package and from subclasses of the class in which they are declared. Protected access can be given by using the protected keyword. |
| Default | Members are accessible from within the same package. Default access can be given without using any keywords. Hence, if we don’t specify public, private, and protected keywords it is default access. |
| Private | Members are only accessible from within the class in which they are declared. Private access can be given by using the private keyword. |
Access Modifier Table in Java
| Access Modifier | Within Class | Within package | Outside package with inheritance | Outside package |
| private | Yes | No | No | No |
| default | Yes | Yes | No | No |
| protected | Yes | Yes | Yes | No |
| public | Yes | Yes | Yes | Yes |
Public Access
What is public access modifiers in Java?
Public access is the least restrictive type of access modifier in Java. Public members are accessible from anywhere in the program.
When should you use public access?
You should use public access for members that you want to be accessible to all classes in the program. For example, you might use public access for methods that are used to interact with the user interface.
Examples of public access
public class MyClass {
public int publicVariable;
public void publicMethod() {
// Do something
}
}Protected Access
What is protected access modifiers in Java?
Protected access is a type of access modifier that is more restrictive than public access. Protected members are accessible from within the same package and from subclasses of the class in which they are declared.
When should you use protected access?
You should use protected access for members that you want to be accessible to subclasses of the class in which they are declared. For example, you might use protected access for members that are used to store data that is shared by subclasses.
Examples of protected access
protected class MyClass {
protected int protectedVariable;
protected void protectedMethod() {
// Do something
}
}Default Access
What is default access modifiers in Java?
Default access is the most restrictive type of access modifier in Java that is not private. Default members are accessible from within the same package.
When should you use default access?
You should use default access for members that you want to be accessible to classes in the same package. For example, you might use default access for members that are used to store data that is shared by classes in the same package.
Examples of default access
class MyClass {
int defaultVariable;
void defaultMethod() {
// Do something
}
}Private Access
What is private access modifiers in Java?
Private access is the most restrictive type of access modifier in Java. Private members are only accessible from within the class in which they are declared.
When should you use private access?
You should use private access for members that you want to keep hidden from other classes. For example, you might use private access for members that are used to store data that is only used by methods in the class.
Examples of private access
private class MyClass {
private int privateVariable;
private void privateMethod() {
// Do something
}
}Conclusion
Access modifiers in Java is an important security mechanism. By using the four types of access modifiers in Java, we can protect the data and code in our program from unauthorized access.
FAQs
What is access modifier in Java?
Access Modifier in Java refers to the mechanism used to restrict or define the visibility and accessibility of classes, methods, and fields in a Java program. It helps determine which parts of a program can be accessed from other classes and which are hidden or restricted.
What are the four access modifiers in Java?
The four access modifiers in Java are:public: Accessible from any other class.private: Accessible only within the same class.protected: Accessible within the same class and its subclasses (inherited classes).default (no modifier): Accessible within the same package (package-private).
What is the default access modifier in Java?
The default access modifier (also known as package-private) is used when no access modifier is specified. It restricts access to classes, methods, or fields to within the same package.
Can a class have multiple access modifiers in Java?
No, in Java, a class can have only one access modifier, and it must match the class’s visibility. However, inner classes can have different access modifiers from their outer classes.
What is the purpose of access modifier in Java?
The primary purpose of access modifier is to enforce encapsulation and protect the integrity of a program’s data and functionality. It allows developers to define which parts of a class are meant to be used by other classes and which should remain private.
Can I override an inherited method with a broader access modifier in Java?
Yes. You can override an inherited method with a broader or same access modifiers in Java. But you can not use weaker or more restricted access modifiers. For example, if your parent class’s method has protected access modifier then you can override it with public access modifier but you can’t use private in overrided method. If using weaker access modifier then the Java compiler will show error message like: attempting to assign weaker access privileges; was protected
What are access modifier rules for interfaces in Java?
In Java interfaces, all methods are implicitly public and fields are implicitly public, static, and final. This means that interface members can be accessed from any class that implements the interface.
Can I access private members of a class from its inner classes?
Yes, inner classes (nested classes) in Java can access the private members of their enclosing (outer) class. This is one of the ways to provide controlled access to private members within a class.
How do you control access to a constructor in Java?
The access modifier of a constructor determines who can create objects of that class. For example, if a constructor is marked as private, objects of that class can only be created within the class itself.