**Concurrency** and **parallelism** both relate to "different things happening more or less at the same time".

But the details between *concurrency* and *parallelism* are quite different.

To see the difference, imagine the following story about burgers:

### Concurrent Burgers

<font color="#3465A4">INFO    </font> Resolved absolute path <font color="#75507B">/home/user/code/awesomeapp/</font><font color="#AD7FA8">main.py</font>
<font color="#3465A4">INFO    </font> Searching for package file structure from directories with <font color="#3465A4">__init__.py</font> files
<font color="#3465A4">INFO    </font> Importing from <font color="#75507B">/home/user/code/</font><font color="#AD7FA8">awesomeapp</font>

                      }));
      assertWrapsInterruptedException(expected);
    } finally {
      interruptenator.shutdown();
      Thread.interrupted();
    }
  }

  /**
   * awaitFullGc() is not quite as reliable a way to ensure calling of a specific finalize method as
   * the more direct await* methods, but should be reliable enough in practice to avoid flakiness of

Let's imagine that you have some **machine learning models** that you want to use to handle requests. 🤖

The same models are shared among requests, so, it's not one model per request, or one per user or something similar.

Let's imagine that loading the model can **take quite some time**, because it has to read a lot of **data from disk**. So you don't want to do it for every request.

export MC_HOST_siteb=http://minioadmin:minioadmin@127.0.0.1:9004

./mc ready sitea
./mc ready siteb

./mc admin replicate add sitea siteb

./mc admin user add sitea foobar foo12345

./mc admin policy attach sitea/ consoleAdmin --user=foobar

./mc admin user info siteb foobar

killall -9 minio

echo "turning off root access, however site replication must continue"
export MINIO_API_ROOT_ACCESS=off

 * </pre>
 * 
 * the access check would fail because the direct ACE has an access mask
 * of <tt>0x001200A9</tt> which doesn't have the
 * <tt>FILE_WRITE_DATA</tt> bit on (bit <tt>0x00000002</tt>). Actually, this isn't quite correct. If
 * <tt>WNET\alice</tt> is in the local <tt>Administrators</tt> group the access check
 * will succeed because the inherited ACE allows local <tt>Administrators</tt>

		done
	fi
	log_end_msg $return
	exit $return
	;;		
  stop)
	log_daemon_msg "Stopping $DESC"

	if [ -f "$PID_FILE" ]; then 
		start-stop-daemon --stop --pidfile "$PID_FILE" \
			--user "$FESS_USER" \
			--quiet \
			--retry forever/TERM/20 > /dev/null
		if [ $? -eq 1 ]; then
			log_progress_msg "$DESC is not running but pid file exists, cleaning up"
		elif [ $? -eq 3 ]; then
			PID="`cat $PID_FILE`"

Nesse caso, você poderia querer documentar como essa API externa *deveria* ser. Que *operação de rota* ela deveria ter, que corpo ela deveria esperar, que resposta ela deveria retornar, etc.

## Um aplicativo com callbacks

Vamos ver tudo isso com um exemplo.

 * </pre>
 * 
 * the access check would fail because the direct ACE has an access mask
 * of <tt>0x001200A9</tt> which doesn't have the
 * <tt>FILE_WRITE_DATA</tt> bit on (bit <tt>0x00000002</tt>). Actually, this isn't quite correct. If
 * <tt>WNET\alice</tt> is in the local <tt>Administrators</tt> group the access check
 * will succeed because the inherited ACE allows local <tt>Administrators</tt>

                return Arrays.equals(this.ansiHash, ntlm.ansiHash) && Arrays.equals(this.unicodeHash, ntlm.unicodeHash);
                /*
                 * This still isn't quite right. If one npa object does not have external
                 * hashes and the other does then they will not be considered equal even
                 * though they may be.
                 */
            }