In Our Last post, we have discussed the OOPS Concepts in Java & In this post of core java tutorial series, we are going to learn about Access Modifiers and how they are work in different scenarios.
What is Access Modifiers?
These are the keywords in Java which set the visibility of a class, interface, variables, data member, method and constructor. That’s why these are also called as Visibility modifiers. It helps to achieve encapsulation because by using access modifiers we can set the control which part of the program can access by the member of a class and by using access modifiers we can avoid misuse of data.
Types of Access Modifiers
In Java Programming Language, we have four types of access modifiers, that are:
- Default – Accessible Within the Package
- Private – Accessible within the class
- Public – Accessible anywhere
- Protected – Accessible within the package and all subclasses
Let’s discuss one by one in briefly:
Default Java
At the time of writing Program, if you are not mentioned any modifiers for a class, interface, variables, data member, method or constructor, then Java by default assign all those with the default access modifiers. And the scope of default access modifiers is within the package only that means you can access the default access modifiers declared variables, classes, method and constructor within the package alone.
Let’s check a program for better understand:
package java_Basics;
class DefaultAccessModifier_Example
{
public static void main(String[] args)
{
System.out.println("This DefaultAccessModifier_Example class");
}
}Private Java
You Can define any data member or method private using the private access modifiers. and those methods or data member are declared as private that are accessible within that class only in which they are declared.
Let’s go through with a program for better understanding
package java_Basics;
class ABC
{
private double num = 100;
private int square(int a)
{
return a*a;
}
}
public class PrivateAccessModifiers_Example
{
public static void main(String[] args)
{
ABC obj = new ABC();
System.out.println(obj.num);
System.out.println(obj.square(10));
}
}
Output:
when you compile the program then that time you will get compile time error
Exception in thread "main" java.lang.Error: Unresolved compilation problems: The field ABC.num is not visible The method square(int) from the type ABC is not visible at java_Basics.PrivateAccessModifiers_Example.main(PrivateAccessModifiers_Example.java:15)
Public Java
Those member or method declared with public modifiers, that are accessible anywhere. That means these modifiers does not put any restriction on the method or data members. Out of all modifiers, the public has the most comprehensive scope among all the modifiers.
Let’s go through with a program for better understanding
package java_Basics;
class PQR
{
public void display()
{
System.out.println("Public Method Of Other Class Executed");
}
}
public class PublicAccessModifiers_Example
{
public static void main(String[] args)
{
PQR obj=new PQR();
obj.display();
}
}Output:
Public Method Of Other Class Executed
Important Points:
- If any other programmer is using your class, then it’s better to give the most restrict access level for particular data member.
- Avoid Public access modifiers public field excepts for constants.
Protected Java
Protected modifiers are specified by the keyword protected. If you assign a data member or methods with protected, then that is accessible by the classes of the same package and the subclasses present in a different package. The protected and default access modifiers are almost the same with only one exception that its visibility in subclasses. You can not declare classes and interfaces as protected, and this protected access modifier is mainly used in a parent-child relationship.
Ref: article
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