That documentation will show up in the Swagger UI at `/docs` in your API, and it will let external developers know how to build the *external API*.

This example doesn't implement the callback itself (that could be just a line of code), only the documentation part.

/// tip

The actual callback is just an HTTP request.

    @Test
    @DisplayName("EmptyIterator should implement CloseableIterator interface")
    void testInterfaceImplementation() {
        // Then
        assertTrue(emptyIterator instanceof CloseableIterator, "Should implement CloseableIterator");
        assertTrue(emptyIterator instanceof Iterator, "Should implement Iterator");
        assertTrue(emptyIterator instanceof AutoCloseable, "Should implement AutoCloseable");
    }

    @Test

                CustomSizeValidator.class.getName());

        // Test that it implements ConstraintValidator
        assertTrue("Should implement ConstraintValidator",
                jakarta.validation.ConstraintValidator.class.isAssignableFrom(CustomSizeValidator.class));
    }

    public void test_methodsExist() {
        // Verify required methods exist

 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code PredecessorsFunction}. It will also work
 * with any other implementation of this interface.
 *
 * <p>If you have your own graph implementation based around a custom node type {@code MyNode},

 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code SuccessorsFunction}. It will also work with
 * any other implementation of this interface.
 *
 * <p>If you have your own graph implementation based around a custom node type {@code MyNode},

 * {@link ValueGraph}, and {@link Network}):
 *
 * {@snippet :
 * someGraphAlgorithm(startNode, graph);
 * }
 *
 * This works because those types each implement {@code SuccessorsFunction}. It will also work with
 * any other implementation of this interface.
 *
 * <p>If you have your own graph implementation based around a custom node type {@code MyNode},

        assertTrue(ex1 instanceof DcerpcError, "DcerpcException should implement DcerpcError");

        // Test that DcerpcException can be created with string messages
        DcerpcException ex2 = new DcerpcException("Access denied error");
        assertTrue(ex2 instanceof DcerpcError, "DcerpcException should implement DcerpcError");

        // Test with root cause

   *
   * <p>A failing {@link TearDown} may or may not fail a tl4j test, depending on the version of
   * JUnit test case you are running under. To avoid failing in the face of an exception regardless
   * of JUnit version, implement a {@link SloppyTearDown} instead.
   *
   * <p>tl4j details: For backwards compatibility, {@code junit3.TearDownTestCase} currently does

name: Feature request
about: Suggest an idea
title: ''
labels: enhancement
assignees: ''

---

Start by telling us what problem you’re trying to solve. Often a solution already exists!

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtCompatible;
import java.util.concurrent.ScheduledFuture;
import org.jspecify.annotations.Nullable;

/**
 * Helper interface to implement both {@link ListenableFuture} and {@link ScheduledFuture}.
 *
 * @author Anthony Zana
 * @since 15.0
 */
@GwtCompatible
public interface ListenableScheduledFuture<V extends @Nullable Object>