ObjectPath.java

import java.util.function.Function;
import java.util.Optional;

interface ObjectPath<T, R> extends Function<T, R> {
  
  default R get(T t) {
    R r = this.apply(t);
    if (r == null) {
      throw new NoSuchElementException();
    }
    return r;
  }
  
  default Optional<R> optionally(T t) {
    return Optional.ofNullable(this.apply(t));
  }
  
  @Override
  default <V> ObjectPath<T, V> andThen(Function<? super R, ? extends V> after) {
    return (s) -> {
      R r = this.apply(s);
      return r != null ? after.apply(r) : null;
    }
  }
  
  default <V> ObjectPath<T, V> specialize(Class<V> specialization) {
    return (s) -> {
      R r = this.apply(s);
      return specialization.isInstance(r) ? (V) r : null;
    }
  } 
}