Abstract classes and interfaces are plentiful in Java code, and even in the Java Development Kit (JDK) itself. Each code element serves a fundamental purpose:
Interfaces are a kind of code contract, which must be implemented by a concrete class.
Abstract classes are similar to normal classes, with the difference that they can include abstract methods, which are methods without a body. Abstract classes cannot be instantiated.
Many developers believe that interfaces and abstract classes are similar, but they are actually quite different. Let’s explore the main differences between them.