for-comprehension: For-comprehension example with three Option suppliers

for-comprehension-with-suppliers.java

private static <T1, T2, T3> ForSupplier3Option<T1, T2, T3> For(Supplier<Option<T1>> ts1, 
                                                               Supplier<Option<T2>> ts2,
                                                               Supplier<Option<T3>> ts3) {
 return new ForSupplier3Option<>(ts1, ts2, ts3);
}
 
public static class ForSupplier3Option<T1, T2, T3> {
  private final Supplier<Option<T1>> ts1;
  private final Supplier<Option<T2>> ts2;
  private final Supplier<Option<T3>> ts3;

  private ForSupplier3Option(Supplier<Option<T1>> ts1, Supplier<Option<T2>> ts2, Supplier<Option<T3>> ts3) {
    this.ts1 = ts1;
    this.ts2 = ts2;
    this.ts3 = ts3;
  }
 
  public <R> Option<R> yield(Function3<? super T1, ? super T2, ? super T3, ? extends R> f) {
    Objects.requireNonNull(f, "f is null");
    return
     ts1.get().flatMap(t1 ->
     ts2.get().flatMap(t2 ->
     ts3.get().map(t3 -> f.apply(t1, t2, t3))));
  }
}