Abstract java | Abstract class in Java | Abstraction in oops-AapKiApniSchool

 

In this blog we will discuss what is Abstract class? How Abstract class is linked with Abstraction? We will check the use of Abstract class in Java. Also we will discuss why do we use Abstract class in Java?We will understand the real scnearion of Abstract class with examples. We will discuss Abstraction in java with example. We will unstandard the purpose of abstraction in OOP and also we will check that we can create constructor in abstract class.

 

Table of Abstract class:

 

  1. What is Abstraction? 

     1.1 Abstraction in java with real time example.

    1.2 How do you achieve abstraction?

  2. Abstract Class

    2.1 Use of Abstract Class

    2.2 Why do we use Abstract class in Java?

   2.3 What is the synatx of Abstract Class in Java?

   2.4 Abstract method in java

  2.5 Where do we use abstract class in real time?

 2.6 Can abstract class have constructor?

 2.7 What is the difference between data hiding and data abstraction?

 

Abstraction in Java: 

Abstraction is a process that hide the implementation and show only functionality. For example you have a car and you know how to drive car but how exactly internally clutch,brake and gear box work, we don't know. And it is not needed for driving car.Here implemetation of clutch,brake and gear is hidden. We know only functionality. Abstract class is sed to implement Abstraction process.

Ways to achieve Abstraction

There are two ways to achieve abstraction in java

 

• Abstract class (0 to 100%)
• Interface (100%)

 

Abstract java:

If any java class is declared with abstract keyword that class is called Abstract class. Abstract class can contain abstract method and non-abstract method. Abstract method means method is declared but don't have any body.Non-Abstract method have body.Abstract method is declared with Abstract keyword. Abstract method can declare only in abstract class.

 

Key Point Of Abstract Class:

 

• It can have abstract and non-abstract methods.
• It can contain static and non-static methods. 
•  We can't create object of abstract class.
•   It can have final methods and constructor. 

 

Use of Abstract class:

 

Abstract class is used for implementing abstraction. It hide the complexity and show only functionality. For example: Car. A car is having  lots of . Like braking system,gear etc. Car is hiding implementation as we don't know how braking systems or gear is working. Without knowing implementation we can use object this is called Abstraction that is implemented by Abstract class.

 

Why do we use Abstract class in Java?

Abstract class in java is used to achive Abstaraction that hide complexity.

 

What is the synatx of Abstract Class in Java?

abstract class A{

}

 

Abstract method in java:

In this class vehicle is an abstract class that is containg one abstract method. This class implementation is given by Car class.

 

abstract class Vehicle{
abstract void run();
}
class Car extends Vehicle{
void run(){System.out.println("Car running safely");}   

public static void main(String args[]){
Vehicle obj = new Car ();
obj.run();
}
}

 

Output:

 Car running safely

 

Abstract class having constructor, data member and methods:

Abstract class can contain constructor,data member,abstract method,non-abstract method and static methods also and even main method.

 

File: Test.java

 

package youtubeClass;

 

public class Test {

 

public static void main(String[] args) {

 Bank bank= new SBI();

 

 System.out.println("Sbi Bank Interest Rate "+bank.getFdInterestRate());

 bank.rbiStndardRules();

 

 bank= new CBI();

 

 System.out.println("Cbi Bank Interest Rate "+bank.getFdInterestRate());

 

 bank.rbiStndardRules();

}

}

 

 

 

File:SBI.java

 

package youtubeClass;

 

public class SBI extends Bank {

 

@Override

int getFdInterestRate() {

int totalInterestRate=minimumInterestRate+5;

return totalInterestRate;

}

 

}

 

 

File: CBI.java

 

package youtubeClass;

 

public class CBI extends Bank {

 

@Override

int getFdInterestRate() {

int totalInterestRate=minimumInterestRate+4;

return totalInterestRate;

}

 

}

 

 

File: Bank.java

 

package youtubeClass;

 

public abstract class Bank {

 

static int minimumInterestRate=10;

public Bank() {

System.out.println("Abstract Class constructor called");

}

 

abstract int getFdInterestRate();

 

void rbiStndardRules()

{

System.out.println("Rbi Standard Rules");

}

 

}

 

 

 

Output:

 

Abstract Class constructor called

Sbi Bank Interest Rate 15

Rbi Standard Rules

Abstract Class constructor called

Cbi Bank Interest Rate 14

Rbi Standard Rules

 

 

Another real scenario of abstract class: 

The best example of abstract class is Java itself as we know the uses of java class but how these classes internally implemented it is hidden for us.

 

 

Can abstract class have constructor?

Abstract class can have constructor, methods with body or Without body(Abstract method). We can not create object of Abstract class.

 

 

What is the difference between data hiding and data abstraction?

 

The main difference is that data hiding is used to secure data but abstraction is used to hide complexity and show only functionality. Data hiding is implemented by encapsulation. Where we encapsulate our data member and methods in single unit. That unit is called class in Java.

 

 

Where do we use abstract class in real time?

 

The best example of abstract class in real time is ATM. We can withdraw money,check balance,register mobile number etc. Without knowing implementation of this operations. It provide the security from unauthorized object. It is showing only functionality and hiding complexity.

 

 

 

 

 

 

 

 

Loops in java-AapKiApniSchool

In this blog we will discuss all 3 type of loop in java in details. We will also discuss Infinite loops also. We will also discuss why for loop better than while loop and difference between while and do while loop. We will go through enhanced for loop that is also known for for-each loop.

Table of content:

1. What are loops?
2. What are the 3 types of loops?
3. What is loop syntax?
4. What is difference between while loop and do while loop?
5. WHY IS FOR loop better than while loop?
6. Which for loop is faster?
7. Which loop is faster in Java?
8. Infinite loop
   1. Infinite for loop
   2. Infinite while loop
   3. Infinite do-while loop
9. Enhanced for loop(for-each loop)

Loops in java:

Loops in Java is used to execute some set of instructions repeatedly when some are conditions.

Types of Loops:

1. for loop
1. Enhanced for loop
2. Infinite for loop
2. while loop
1. Infinite while loop
3. do while loop
1. Infinite do while loop

For loop:

For loop is a short hand of writing loop. It consists initialization,condition and increament/decreapment in one line.

Syntax:

  for(initlozation;condition;increment/decreament)
{

}

Flow chart:

Initialization:

In Initialization we provide the initial value of variable to start loop. We can use already declared variable or we can create new variable.

Condition:

Before executing loop first condition value is checked if condition is true then only block of loop is executed else loop terminated. Condition is mainly used to terminate loop after a particular condition failed.

Increment/decrement:

After executing first iteration variable value is increment or decrement and again condition checked.

Enhanced For loop:

In java 5 we got enhancement of for loop. Enhanced for loop is providing a simple way for iterating collection or array. Enhanced for loop is used only when you want to iterate a array or collection in a sequential manner without knowing index. Enhanced for loop is also know is for-each loop. It increase readability. Best drawback of for each loop is when iterating any array or collection we can't skip any element or we can't traverse in reverse order.

for(data_type variable : array | collection){  
//body of for-each loop  
} 

package testjava;

import java.util.ArrayList;
import java.util.List;

public class TestLoop {

	public static void main(String[] args) {
		
		List list= new ArrayList<>();

		list.add("Sunil");
		list.add("Anil");
		list.add("Narendra");
		
		for(String x:list)
		{
			System.out.println(x);
		}
	}

}

Output:
Sunil
Anil
Narendra

Java Infinite for loop:

If you don't pass Initialization, condition and increment/decrement value in for loop then it will be infinite for loop.

for(;;)
{}

While loop:

While loop first check condition, if condition is true then it will execute the body of loop otherwise terminate loop. While loop is used when iteration is not fixed. While loop also known for Entry check loop.

   while(condition)
   {
      //loop body
   }
  

Java Infinitive While Loop:

if you pass true in condition then it will be infinite while loop. It will never terminate.
 

    package testjava;

public class TestLoop {

	public static void main(String[] args) {
	
		while(true)
		{
			System.out.println("number ");
		
		}
	}

}

  

Note: If you want to stop infinite loop then press Ctrl+C

do while:

do while loop first execute the body after that check condition. If condition is true then again it will execute iteration. do while loop execute at least one time if condition is true or not. In do while loop for first execution condition is not checked.

    
<1 pre="">
package testjava;

public class TestLoop {

	public static void main(String[] args) {
	int i=1;
		do {
			System.out.println("Number is "+i);
		}while(i<1);
	}

}

<1 pre="">

<1 pre="">Output:

<1 pre="">

<1 pre="">Number is 1
Java Infinitive do-while Loop
If you pass true in the do-while loop, it will be infinitive do-while loop.


Syntax:

do{  
//code to be executed  
}while(true);  

<1 pre="" style="background-color: powderblue;">package testjava;

public class TestLoop {

	public static void main(String[] args) {
	
		do {
			System.out.println("Number");
		}while(true);
	}

}

Note: If you want to stop infinite loop then press Ctrl+C

What is difference between while loop and do while loop?

While loop first check condition if condition is true then execute the body of loop but do-while loop first execute the body and then check condition if condition is true then it will condition execute loop. Do-While loop execute at least one time if condition is false or true. While loop can execute 0-n time but Do-While loop execute 1-n times.

WHY IS FOR loop better than while loop?

Performance of for loop and while loop is same. The advantage of a for loop is that it's harder to accidentally do an infinite loop. Or rather, it's more obvious when you do one because you generally put the loop var in the initial statement. If we know the iteration then we should use for loop. If we don't know the iteration then we should use while loop. For example reading a file.