Assign generic method to variable in Scala

will help you I'm not entirely sure what your actual goal is. I guess what you are trying to achieve seem to be better solved by filter and map:
filter serves as validator in this case, i.e., people.filter(isFirstNameValid). This returns a collection of all people with a defined first name -- is this what you want? map serves as extractor of the desired field, in this case the first name. So overall people.filter(isFirstNameValid).map(_.firstName) in case you want your collection to represent first names instead of a complete person. If you furthermore want to convert from Option (of first name) to a concrete value you may want to use flatMap instead (this also makes the explicit validation unnecessary).

I wish this help you I'm trying to use Generic interfaces for my classes. My Class has a generic Type which Extends an interface and a class variable with that Type. But as soon as I try to assign a value to that variable the compiler gives me an error.(Example: Class A)

class A<IState extends MyStateInterface> {
    protected state: IState;

    constructor() {
        this.state = { ...

interface MyCoolState extends MyStateInterface {
  required: string;
}
let x = new A<MyCoolState>();

Does that help Let's say we've got the following classes:

public void onServiceEvent(ServiceEvent event) {}

EventListener<ServiceEvent> listener = service::onServiceEvent;

EventListener<? extends Event> anotherListener

wish helps you You were close. You need two generic types: a type for your object (bean), and a type for the value. You want a BiConsumer, not a Function, because a set-method does not return anything.

public static <T, V> T assignValueToAttribute(T obj, BiConsumer<T, V> attributeSetter, V value) {
    attributeSetter.accept(obj, value);
    return obj;
}

assignValueToAttribute(myCar, Car::setColor, "red");

should help you out Welcome to SO.
This seems to compile, but I am not sure if it works with the real implementation of JavaClass, but I am pretty sure it should.

import scala.reflect.ClassTag

object ScalaClass {
  def toArray[T <: AnyRef](coll: java.util.Collection[T])(implicit ct: ClassTag[T]): Array[T] =
    JavaClass.toArray[T](ct.runtimeClass.asInstanceOf[Class[T]], coll)
}

val col: java.util.Collection[String] = ???

val array: Array[String] = ScalaClass.toArray(col)

object ScalaClass {
  def toArray[T <: AnyRef](t: java.lang.Class[T], coll: java.util.Collection[T]): Array[T] =
    JavaClass.toArray[T](t, coll)
}

val col: java.util.Collection[String] = ???

val array: Array[String] = ScalaClass.toArray(classOf[String], col)