// operation in the constructor.
  //
  // 1. In the listener that performs the callback. In this case it is fine since inputFuture is
  //    assigned prior to calling addListener, and addListener happens-before any invocation of the
  //    listener. Notably, this means that 'volatile' is unnecessary to make 'inputFuture' visible
  //    to the listener.
  //

showEvent = EventHandler.trigger(this._element, EVENT_SHOW, relatedTarget)\n\n    if (showEvent.defaultPrevented) {\n      return\n    }\n\n    this._createPopper()\n\n    // If this is a touch-enabled device we add extra\n    // empty mouseover listeners to the body's immediate children;\n    // only needed because of broken event delegation on iOS\n    // https://www.quirksmode.org/blog/archives/2014/02/mouse_event_bub.html\n    if ('ontouchstart' in document.documentElement && !this._parent.cl...

{\n        $(parent).addClass(CLASS_NAME_POSITION_STATIC)\n      }\n\n      this._popper = new Popper(referenceElement, this._menu, this._getPopperConfig())\n    }\n\n    // If this is a touch-enabled device we add extra\n    // empty mouseover listeners to the body's immediate children;\n    // only needed because of broken event delegation on iOS\n    // https://www.quirksmode.org/blog/archives/2014/02/mouse_event_bub.html\n    if ('ontouchstart' in document.documentElement &&\n        $(paren...

    queue.enqueue(incrementingEvent(counters, listener1, 1));
    queue.enqueue(incrementingEvent(counters, listener1, 2));

    Object listener2 = new Object();
    queue.addListener(listener2, directExecutor());
    queue.enqueue(incrementingEvent(counters, multiset(listener1, 3, listener2, 1)));
    queue.enqueue(incrementingEvent(counters, multiset(listener1, 4, listener2, 2)));
    assertEquals(0, counters.size());
    queue.dispatch();

    queue.enqueue(incrementingEvent(counters, listener1, 1));
    queue.enqueue(incrementingEvent(counters, listener1, 2));

    Object listener2 = new Object();
    queue.addListener(listener2, directExecutor());
    queue.enqueue(incrementingEvent(counters, multiset(listener1, 3, listener2, 1)));
    queue.enqueue(incrementingEvent(counters, multiset(listener1, 4, listener2, 2)));
    assertEquals(0, counters.size());
    queue.dispatch();

        // Test with listener1
        factory.setOnDestroyListener(listener1);
        assertEquals(listener1, factory.getOnDestroyListener());
        factory.destroyObject(pooledObject);
        assertEquals(1, events.size());
        assertEquals("listener1", events.get(0));

        // Switch to listener2
        factory.setOnDestroyListener(listener2);
        assertEquals(listener2, factory.getOnDestroyListener());

        // Add second listener (should replace first)
        TestShutdownListener listener2 = new TestShutdownListener();
        scriptExecutor.addShutdownListener(listener2);

        // Call shutdown
        scriptExecutor.shutdown();

        // Verify only second listener was called
        assertFalse(listener1.wasShutdownCalled());
        assertTrue(listener2.wasShutdownCalled());

        };

        ShutdownListener listener2 = new ShutdownListener() {
            @Override
            public void onShutdown() {
                callCount.addAndGet(10);
            }
        };

        // Add first listener
        jobExecutor.addShutdownListener(listener1);
        assertEquals(listener1, jobExecutor.shutdownListener);

        // Replace with second listener

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;

/**
 * A listener for session events.
 * TODO: open this to other events like similar to {@code org.apache.maven.eventspy.EventSpy}
 *
 * @since 4.0.0
 */
@Experimental
@FunctionalInterface
@Consumer
public interface Listener {
    void onEvent(@Nonnull Event event);

import org.apache.maven.api.annotations.Experimental;
import org.apache.maven.api.annotations.Nonnull;

/**
 * Event sent by maven during various phases of the build process.
 * Such events can be listened to using {@link Listener}s objects
 * registered in the {@link Session}.
 *
 * @since 4.0.0
 */
@Experimental
public interface Event {

    /**
     * Gets the type of the event.
     *