startUpCalled = true;
      throw new UnsupportedOperationException("kaboom!");
    }

    @Override
    protected void run() {
      throw new AssertionError("run() should not be called");
    }

    @Override
    protected Executor executor() {
      return exceptionCatchingExecutor;
    }
  }

  public void testServiceThrowOnRun() throws Exception {

  }

  /**
   * Gets an iterator representing an immutable snapshot of all subscribers to the given event at
   * the time this method is called.
   */
  Iterator<Subscriber> getSubscribers(Object event) {
    ImmutableSet<Class<?>> eventTypes = flattenHierarchy(event.getClass());

    List<Iterator<Subscriber>> subscriberIterators =

          }
        } else if (result.isError()) {
          // Only reach here if a CharsetEncoder with non-REPLACE settings is used.
          result.throwException();
          return 0; // Not called.
        }
      }
    }
  }

  /** Returns a new CharBuffer identical to buf, except twice the capacity. */
  private static CharBuffer grow(CharBuffer buf) {

          }
        } else if (result.isError()) {
          // Only reach here if a CharsetEncoder with non-REPLACE settings is used.
          result.throwException();
          return 0; // Not called.
        }
      }
    }
  }

  /** Returns a new CharBuffer identical to buf, except twice the capacity. */
  private static CharBuffer grow(CharBuffer buf) {

    return getAndUpdate(key, x -> newValue);
  }

  /**
   * Copies all of the mappings from the specified map to this map. The effect of this call is
   * equivalent to that of calling {@code put(k, v)} on this map once for each mapping from key
   * {@code k} to value {@code v} in the specified map. The behavior of this operation is undefined
   * if the specified map is modified while the operation is in progress.

* A particular program while it is **running** on the operating system, using the CPU, and storing things on memory. This is also called a **process**.

### What is a Process

The word **process** is normally used in a more specific way, only referring to the thing that is running in the operating system (like in the last point above):

          }

          @Override
          @SuppressWarnings("ThreadPriorityCheck") // doing our best to test for races
          public Boolean get() {
            // Check that this method is called exactly once, by the first
            // thread to synchronize.
            long t0 = System.nanoTime();
            while (waitingThreads() != numThreads - 1) {
              if (System.nanoTime() - t0 > timeout) {

          }

          @Override
          @SuppressWarnings("ThreadPriorityCheck") // doing our best to test for races
          public Boolean get() {
            // Check that this method is called exactly once, by the first
            // thread to synchronize.
            long t0 = System.nanoTime();
            while (waitingThreads() != numThreads - 1) {
              if (System.nanoTime() - t0 > timeout) {

          boolean firstCall = true;

          @Override
          public boolean processBytes(byte[] buf, int off, int len) throws IOException {
            assertTrue("consume() called twice", firstCall);
            firstCall = false;
            return false;
          }

          @Override
          public @Nullable Void getResult() {
            return null;
          }

One particular advantage that is not necessarily obvious is that you can **generate clients** (sometimes called <abbr title="Software Development Kits">**SDKs**</abbr> ) for your API, for many different **programming languages**.

## OpenAPI Client Generators

There are many tools to generate clients from **OpenAPI**.