Differences between abstract class and concrete class in Java

In Java, abstraction is achieved using Abstract classes and interfaces. An abstract class contains abstract methods which a child class. Following are the important differences between abstract class and a concrete class.

Sr. No.	Key	Abstract Class	Concrete Class
1	Supported Methods	Abstract class can have both an abstract as well as concrete methods.	A concrete class can only have concrete methods. Even a single abstract method makes the class abstract.
2	Instantiation	Abstract class can not be instantiated using new keyword.	Concrete class can be instantiated using new keyword.
3	Abstract method	Abstract class may or may not have abstract methods.	Concrete clas can not have an abstract method.
4	Final	Abstract class can not be declared as a final class.	Concrete class can be declared final.
5	Keyword	Abstract class declared using abstract keyword.	Concrete class is not having abstract keyword during declaration.
6	Inheritance	Abstract class can inherit another class using extends keyword and implement an interface.	Interface can inherit only an inteface.
7	Interface	Abstract class can not implement an interface alone. A child class is needed to be able to use the interface for instantiation.	Interface can be implemented easily.

Example of Abstract Class vs Concrete Class

JavaTester.java

public class JavaTester {
   public static void main(String args[]) {
      Cat lion = new Lion();
      lion.eat();
   }
}
abstract class Cat {
   abstract public void eat();
}
class Lion extends Cat{
   public void eat(){
      System.out.println("Lion eats");
   }
}

Output

Lion eats