Access modifiers in Java
Access modifiers in Java with Example
In Java, there are two types of access modifiers one is a non-access modifier, and other is access modifier.
If we talk about access modifier, there are four types of access modifier.
- default
- private
- public
- protected
Access modifier restricts the access of data members, methods, class, and constructors.
Access modifiers also specify the access level of classes, variable methods, and constructor.
default access modifier
When no modifier is specified for a class, method, or data member then Java compiler consider it as default modifier.
The class, data members or methods having default access modifier are accessible only within the same package.
Example
A.java
package core2;
class A{
void disp(){System.out.println("Hiii…");}
}
B.java
package core1;
import core2.*;
class B{
public static void main(String args[]){
A obj = new A();//Compilation Error
obj.disp();//compilation Error
}
}
Output
Compile time error
In the given example, access modifier (Scope) of A and the given method disp() are default then both are accessible within the same package. We are using two different package core1 and core2 so this program will throw a compilation error.
Java Private access modifier
It is a class level modifier; in other words, the scope of private modifier is limited to the class only. Some essential points about private access modifier are:
- Methods and private data members are only accessible within the class.
- In Java, a class and interface cannot be declared as private.
- If we declare a constructor as private, then we cannot create the object of that class from outside of the class.
Example
class A{
private int n=40;
private void disp(){System.out.println("This is a private method");}
}
public class Demo{
public static void main(String args[]){
A obj=new A();
System.out.println(obj.n);//Compile Time Error
obj.disp();//Compile Time Error
}
}
Output
Compile time error
In the given example, we are trying to access private data member n and private method disp() from outside the class. So it will lead to compilation error.
Java Private constructor
Example
class A{
private A(){}//private constructor
void disp(){System.out.println("in constructor A");}
}
public class Demo{
public static void main(String args[]){
A obj=new A();//Compile Time Error
}
}
Output
Compile time error
In the given an example, we have declared a constructor A() as private, so we cannot create the instance of class A. it will lead to a compilation error.
Java public access modifier
The public access modifier has the widest scope among all other modifiers. It can be accessed from everywhere. It is specified using the keyword "public."
Example
A1.java
package core2;
public class A1{
public void disp(){System.out.println("This is public modifier");}
}
B.java
package core1;
import core2.*;
class B{
public static void main(String args[]){
A1 obj = new A1();
obj.disp();
}
}
Output
This is public modifier
- Try to use most restrictive access level that makes sense for a particular member therefore always Use private modifier unless you have a good reason not to.
- Try to avoid public fields except for constants.
Java Protected access modifier
The "protected" keyword is used to specify the protected access modifier. It is accessible within the same package or outside the package through inheritance.
A1.java
package core2;
public class A1{
protected void disp(){System.out.println("in protected method disp");}
}
B1.java
package core1;
import core2.*;
class B1 extends A1{
public static void main(String args[]){
B1 obj = new B1();
obj.disp();
}
}
Output
in protected method disp