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

### Concurrent Burgers { #concurrent-burgers }

You go with your crush to get fast food, you stand in line while the cashier takes the orders from the people in front of you. 😍

<img src="/img/async/concurrent-burgers/concurrent-burgers-01.png" class="illustration">

import java.nio.charset.UnsupportedCharsetException;
import java.util.ConcurrentModificationException;
import java.util.NoSuchElementException;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;
import junit.framework.AssertionFailedError;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

import java.util.Deque;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
import java.util.concurrent.Semaphore;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicInteger;

 */

package com.google.common.util.concurrent;

import static com.google.common.base.Verify.verify;
import static com.google.common.truth.Truth.assertThat;
import static com.google.common.util.concurrent.Futures.immediateFailedFuture;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import jcifs.CIFSContext;
import jcifs.Configuration;

import com.google.common.util.concurrent.ListenableScheduledFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.Callable;
import java.util.concurrent.Delayed;

import com.google.common.util.concurrent.ListenableScheduledFuture;
import com.google.common.util.concurrent.ListeningExecutorService;
import com.google.common.util.concurrent.ListeningScheduledExecutorService;
import java.util.Collection;
import java.util.List;
import java.util.concurrent.AbstractExecutorService;
import java.util.concurrent.Callable;
import java.util.concurrent.Delayed;

 */

package com.google.common.util.concurrent;

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.util.concurrent.Futures.getUnchecked;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.CHECKED_EXCEPTION;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.ERROR;

 */

package com.google.common.util.concurrent;

import static com.google.common.truth.Truth.assertThat;
import static com.google.common.util.concurrent.Futures.getUnchecked;
import static com.google.common.util.concurrent.Futures.immediateFuture;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.CHECKED_EXCEPTION;
import static com.google.common.util.concurrent.FuturesGetCheckedInputs.ERROR;

- **Logging Abstraction** (`org.codelibs.core.log`) - Flexible logging system supporting JCL (Jakarta Commons Logging) and JUL (Java Util Logging)
- **Concurrent Utilities** (`org.codelibs.core.concurrent`) - Thread-safe collections and concurrency helpers using modern concurrent APIs
- **Crypto & Security** (`org.codelibs.core.crypto`, `org.codelibs.core.security`) - Basic cryptographic utilities, message digest operations, and secure random generation