Access modifiers in Java define the scope of accessibility for classes, methods, and variables. Understanding these is essential for encapsulation, security, and code organization.
They control how the members of a class can be accessed from other classes or packages.
Java provides four types of access modifiers:
Choosing the correct access modifier helps in protecting data and methods from unintended access.
Clear explanation of public, private, protected, and default modifiers.
// Example demonstrating access modifiers
package com.example;
public class AccessDemo {
public int publicVar = 10; // accessible everywhere
private int privateVar = 20; // accessible only in this class
protected int protectedVar = 30; // accessible in package & subclasses
int defaultVar = 40; // accessible only in package
public void show() {
System.out.println("publicVar: " + publicVar);
System.out.println("privateVar: " + privateVar);
System.out.println("protectedVar: " + protectedVar);
System.out.println("defaultVar: " + defaultVar);
}
}
// In the same package, another class can access publicVar, protectedVar, and defaultVar,
// but NOT privateVar.
// In different package
package com.test;
import com.example.AccessDemo;
public class SubClass extends AccessDemo {
public void display() {
System.out.println(publicVar); // Accessible
// System.out.println(privateVar); // Error: Not accessible
System.out.println(protectedVar); // Accessible in subclass
// System.out.println(defaultVar); // Error: Not accessible outside package
}
}
Access modifiers are key to data hiding, preventing unauthorized access and modifications.
They help organize code into packages and modules with clear boundaries.
Control which members are inherited or visible to subclasses.
public members are accessible from any other class, whereas private members are accessible only within their own class.
Use protected when you want members accessible to subclasses and classes within the same package, but hidden from other classes.
Default (package-private) access applies when no modifier is specified. Members are accessible only within the same package.