* asynchronously.
 *
 * <p>To attach to a {@link ListenableFuture} use {@link Futures#addCallback}.
 *
 * @author Anthony Zana
 * @since 10.0
 */
@GwtCompatible
public interface FutureCallback<V extends @Nullable Object> {
  /** Invoked with the result of the {@code Future} computation when it is successful. */
  void onSuccess(@ParametricNullness V result);

  /**

    addCallback(f, callback, directExecutor());
    f.setException(e);
  }

  public void testCancel() {
    SettableFuture<String> f = SettableFuture.create();
    FutureCallback<String> callback =
        new FutureCallback<String>() {
          private final Object monitor = new Object();
          private boolean called = false;

          @Override
          public void onSuccess(String result) {

import org.apache.hc.client5.http.async.methods.SimpleHttpRequests
import org.apache.hc.client5.http.async.methods.SimpleHttpResponse
import org.apache.hc.client5.http.impl.async.HttpAsyncClients
import org.apache.hc.core5.concurrent.FutureCallback
import org.apache.hc.core5.http.ProtocolVersion
import org.junit.Assert
import org.junit.Test

/**
 * Simplified from

  }

  public void testAddCallback() {
    FluentFuture<String> f = FluentFuture.from(immediateFuture("a"));
    boolean[] called = new boolean[1];
    f.addCallback(
        new FutureCallback<String>() {
          @Override
          public void onSuccess(String result) {
            called[0] = true;
          }

          @Override
          public void onFailure(Throwable t) {}
        },