Abstract Class and Interface are used to achieve Abstraction where abstract methods are declared. We can’t instantiate Abstract Class and Interface.
| Abstract Class | Interface |
| Abstract Class can have both abstract method and non-abstract methods. | Interface can have only abstract methods. |
| Abstract Class does not support multiple Inheritance. | Interface supports multiple Inheritance. |
| Abstract Class can be implemented by using keyword “extends”. | Interface can be implemented by using keyword “implements”. |
| Abstract class can provide the implementation of interface. | Interface can’t provide the implementation of abstract class. |
| Abstract Class can have static, non-static, final & non-final variables. | Interface can have only final & static variables. |
| Abstract Class can have class members as private, protected, etc. | Interface can have class members as public by default. |
| Example: public abstract class Shape{ public abstract void draw(); } | Example: public interface Drawable{ void draw(); } |
| An abstract class can extend another Java class and implement multiple Java interfaces. | An interface can extend another Java interface only. |
| Abstract keyword is used to declared abstract class | Interface keyword is used to declare interface. |
Below is an example of Abstract Class. In the below example, there is an abstract class with abstract method. This abstract method is implemented in SubClass.
//Abstract Class
public abstract class Bank {
// Abstract method
abstract void getRateOfInterest();
}
SubClass
//Subclass (inherit from Bank)
public class SBI extends Bank {
// The body of getRateOfInterest is declared here
public void getRateOfInterest() {
System.out.println("Interest Rate of SBI Bank :" + 5.3);
}
}
Test Class
public class AbstractionTest {
public static void main(String[] args) {
Bank bank1 = new SBI();
bank1.getRateOfInterest();
}
}
Below is an example of Interface. In the below example, Interface has two abstract methods and the implementation of abstract methods are declared in Test Class.
public interface MyInterface {
// Abstract methods
public void method1();
public void method2();
}
Test Class
public class InterfaceTest implements MyInterface {
public void method1() {
System.out.println("Implementation of Method 1");
}
public void method2() {
System.out.println("Implementation of Method 2");
}
public static void main(String[] args) {
MyInterface interTest = new InterfaceTest();
interTest.method1();
interTest.method2();
}
}
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