The difference between abstract classes and interfaces in Java

In Java, abstraction is achieved through abstract classes and interfaces. Both contain abstract methods that subclasses or implementing classes must implement. Following are the important differences between abstract class and interface.

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Abstract class and interface example

JavaTester.java

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

Output

Tiger eats
Lion eats

Sr. No.	Key	Abstract class	Interface
1	Supported methods	Abstract classes can have both abstract methods and concrete methods.	Interfaces can only have abstract methods. Starting from Java 8, it can have default and static methods.
2	Multiple inheritance	Multiple inheritance is not	Interface supports multiple inheritance.
3	Supported variables	Supports final, non- Final, static and non-static variables.	Only static and final variables are allowed.
4	Implementation	Abstract classes can implement interfaces.	The interface does not need to implement the interface, or it can extend the interface.
5	Keyword	Use abstract keyword declaration abstract class.	The interface is declared using the interface keyword.
6	Inheritance	Abstract classes can inherit from another Classes use the extends keyword and implement interfaces.	Interfaces can only inherit interfaces.
Inheritance	Abstract classes can use the extends key Word inheritance.	Interfaces can only be implemented using the implements keyword.
8	Access	Abstract classes can have any type members, such as private and public.	Interfaces can only have public members.

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