Java Optional that forces you to deal with the missing value on compile-time level instead of the runtime.

CheckedOptional.java

package org.example;

import java.util.Optional;
import java.util.Random;
import java.util.function.Supplier;

class NPEChecked extends Exception implements Supplier<NPEChecked> {
  private static final NPEChecked instance = new NPEChecked();

  @Override
  public NPEChecked get() {
    return instance;
  }

  public static NPEChecked supplier() {
    return instance;
  }
}

public class Main {

  private static Integer saferOptionals() throws NPEChecked {
    return (new Random().nextBoolean() ? Optional.of(42) : Optional.<Integer>empty())
        .orElseThrow(NPEChecked.supplier());
  }

  public static void main(String... args) {
    try {
      Integer x = saferOptionals();
      System.out.printf("It was Some(%d)%n", x);
    } catch (NPEChecked e) {
      System.out.println("It was None");
    }
  }

  /*
   * You can always re-throw the checked exception to the next caller. 
   * Unfortunately to transform the `None` into something resembling `Left(err)` 
   * you'd have to catch and throw new exception. 
   *
   * It becomes very verbose very fast 🙀.
  */
  public static void main2(String... args) throws NPEChecked {
    Integer x = saferOptionals();
  }
}