day-26: Encapsulation and Abstraction in Java

Encapsulation:
In Java that involves bundling the data (variables) and the methods (functions) that operate on the data into a single unit, known as a class. It restricts direct access to some of an object's components and can prevent the accidental modification of data.

1) private - Accessible within the same class only 2) default - Accessible within the same package (no keyword used) 3) protected - Accessible within the same package AND subclasses in other packages 4) public - Accessible from anywhere 

Use this When you...
--> import Want to use a class from a different package
--> extends Want to inherit functionality from another class

Example code for protected:

package housingloandpackage; public class HDFC { protected void education_load () { System.out.println("Educational load"); } public static void main(String[] args) { // TODO Auto-generated method stub } } package educationloanpackage; import housingloandpackage.HDFC; public class IOB extends HDFC { public static void main(String[] args) { IOB iob = new IOB(); iob.education_load(); } } package educationloanpackage; import housingloandpackage.HDFC; public class SBI { public static void main(String[] args) { HDFC hdfc = new HDFC(); hdfc.emp_salary(); } } 

IS-A Relationship only we can use extends key.
Note:
--> If we extent the class we can use our own object
or else we need to create new object for the class.

Abstraction
Abstraction in Java is a fundamental object-oriented programming concept that involves hiding complex implementation details and presenting only the essential features to the user.

public abstract class Parents { public abstract void study(); public void grow() { System.out.println("Take Care"); } public static void main(String[] args) { //Parents parents = new Parents(); //parents.study(); Can't do that. } } 

Here:
1). Class and Method can be abstract.
2). It cannot be instantiated directly. - Can't create Object.
3). If at least one method is abstract in a class, then the entire class should be abstract
4). Abstract classes cannot be instantiated, but they can be subclassed.

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