Abstract class vs Interface: The Interface Strikes Back!

Previously, methods with implementations could only exist in abstract classes, but starting from Java 8, they also appeared in interfaces.

Let's take a look at the syntax for declaring a default method:

We need default methods for the same purposes as regular methods in Java. We use them when we need an implementation in the method and when we want to implement only the interface without additional classes. Let's consider a small example using default methods:

In this example, the interface Greeting contains a default method sayHello() with a default implementation. The class GreetingImpl implements this interface and overrides the greet() method. In the main method, an instance of GreetingImpl is created and both methods are called.