Default methods in Java interfaces give a slightly similar feeling to Kotlin extension functions, but they are not the same thing

InterfaceDefaultMethod.java

public class Main {
    public static void main(String[] args) {
        User user = new User("Dora");
        System.out.println(user.getGreeting());
    }
}

interface UserOps {
    default String getGreeting() {
        return "Hello, " + getName() + "!";
    }

    String getName();
}

class User implements UserOps {
    private final String name;

    public User(String name) {
        this.name = name;
    }

    @Override
    public String getName() {
        return name;
    }
}