What are access modifiers in Java?

Access Modifiers in Java

Access modifiers in Java are keywords that control the visibility and accessibility of class members (fields, methods, constructors, and nested classes) within a Java program. Java provides four access modifiers: public, private, protected, and default (also known as package-private).

Public Access Modifier

The public access modifier is the most permissive access level. A class, method, or field declared as public can be accessed from anywhere in the program, including other classes, packages, and subclasses.

Example:

public class MyClass {
    public int publicField;
    public void publicMethod() {
        // This method can be accessed from anywhere
    }
}

Private Access Modifier

The private access modifier is the most restrictive access level. A class member declared as private can only be accessed within the same class in which it is defined. It is not accessible from subclasses or other classes.

Example:

public class MyClass {
    private int privateField;
    private void privateMethod() {
        // This method can only be accessed within the same class
    }
}

Protected Access Modifier

The protected access modifier allows access to class members within the same package and also from subclasses, even if they are in different packages.

Example:

public class SuperClass {
    protected int protectedField;
    protected void protectedMethod() {
        // This method can be accessed within the same package
        // and from subclasses
    }
}

public class SubClass extends SuperClass {
    // Can access the protected members from the SuperClass
}

Default (Package-Private) Access Modifier

If no access modifier is explicitly specified, the default (or package-private) access modifier is used. Class members with the default access modifier can be accessed by other classes within the same package, but not from outside the package.

Example:

class MyClass {
    int defaultField;
    void defaultMethod() {
        // This method can be accessed by other classes
        // within the same package
    }
}

graph TD A[Access Modifiers in Java] A --> B[public] A --> C[private] A --> D[protected] A --> E[default (package-private)] B --> F[Accessible from anywhere] C --> G[Accessible only within the same class] D --> H[Accessible within the same package and subclasses] E --> I[Accessible within the same package]

In summary, access modifiers in Java provide a way to control the visibility and accessibility of class members, allowing you to encapsulate your code and prevent unauthorized access. Understanding and properly using access modifiers is a fundamental aspect of Java programming and object-oriented design.