}

  private Absent() {}

  @Override
  public boolean isPresent() {
    return false;
  }

  @Override
  public T get() {
    throw new IllegalStateException("Optional.get() cannot be called on an absent value");
  }

  @Override
  public T or(T defaultValue) {
    return checkNotNull(defaultValue, "use Optional.orNull() instead of Optional.or(null)");
  }

    return forward.iterator();
  }

  @Override
  @GwtIncompatible("NavigableSet")
  ImmutableSortedSet<E> createDescendingSet() {
    throw new AssertionError("should never be called");
  }

  @Override
  public @Nullable E lower(E element) {
    return forward.higher(element);
  }

  @Override
  public @Nullable E floor(E element) {
    return forward.ceiling(element);
  }

import kotlin.reflect.KClass

/**
 * An immutable collection of key-value pairs implemented as a singly-linked list.
 *
 * Build up a collection by starting with [EmptyTags] and repeatedly calling [plus]. Each such call
 * returns a new instance.
 *
 * This collection is optimized for safe concurrent access over a very small number of elements.
 *

     */
    @Override
    public boolean markSupported() {
        return fileInputStream.markSupported();
    }

    /**
     * Repositions this stream to the position at the time the mark method was last called on this input stream.
     * This method delegates to {@link FileInputStream#reset()}.
     *
     * @throws IOException if an I/O error occurs.
     */
    @Override

This means that instead of the normal process of your users sending requests to your API, it's **your API** (or your app) that could **send requests to their system** (to their API, their app).

This is normally called a **webhook**.

## Webhooks steps { #webhooks-steps }

The process normally is that **you define** in your code what is the message that you will send, the **body of the request**.

 * resulting in notification could have occurred to an entry being manually removed or replaced, or
 * due to eviction resulting from timed expiration, exceeding a maximum size, or garbage collection.
 *
 * <p>An instance may be called concurrently by multiple threads to process different entries.
 * Implementations of this interface should avoid performing blocking calls or synchronizing on
 * shared resources.
 *

        when(src.openUnshared(eq(0), eq(SmbConstants.O_RDONLY), eq(SmbConstants.FILE_SHARE_READ), eq(SmbConstants.ATTR_NORMAL), eq(0)))
                .thenReturn(sfd);

        // openCopyTargetFile should be called by serverSideCopy, so dest.openUnshared must succeed
        SmbFileHandleImpl dfd = mock(SmbFileHandleImpl.class);
        when(dest.openUnshared(anyInt(), anyInt(), anyInt(), anyInt(), anyInt())).thenReturn(dfd);

            UpgradeResult result = orchestrator.executeStrategies(context, pomMap);

            assertTrue(result.success(), "Orchestrator should succeed when all strategies succeed");

            // Verify all strategies were called
            for (UpgradeStrategy strategy : mockStrategies) {
                verify(strategy).isApplicable(context);
                verify(strategy).apply(Mockito.eq(context), Mockito.any());
            }
        }

## `PATH` Environment Variable { #path-environment-variable }

There is a **special** environment variable called **`PATH`** that is used by the operating systems (Linux, macOS, Windows) to find programs to run.

                  throw new IllegalArgumentException("Multiple values for key: " + v1 + ", " + v2);
                }),
        (accum, t) -> {
          /*
           * We assign these to variables before calling checkNotNull to work around a bug in our
           * nullness checker.
           */
          K key = keyFunction.apply(t);
          V newValue = valueFunction.apply(t);
          accum.put(