How to Create an Instance of an Anonymous Interface in Kotlin?

How can I create an instance of the Handler interface anonymously in Kotlin while achieving similar functionality as in Java?

public interface Handler<C> {
  void call(C context) throws Exception;
}

In Kotlin, you can implement Java interfaces such as Handler using lambda expressions or object expressions, which provide concise syntax similar to Java's anonymous classes. This allows for cleaner code while maintaining functionality.

val handler = object : Handler<MyContext> {
    @Throws(Exception::class)
    override fun call(context: MyContext) {
        println("Hello world")
    }
}

handler.call(myContext) // Prints "Hello world"

Solutions

• To implement the `Handler` interface in Kotlin, use an object expression. This accomplishes the same as a Java anonymous class.
• Here's how you can define and use the `Handler` interface in Kotlin:

Mistake: Not including `@Throws(Exception::class)` annotation in Kotlin when overriding methods that throw exceptions.

Solution: Ensure to use @Throws to properly handle exceptions when implementing Java interfaces in Kotlin.

Mistake: Forgetting to use `override` keyword when implementing methods from an interface.

Solution: Always include the `override` keyword for methods that are part of an interface implementation.