* or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */

package com.google.common.util.concurrent;

import com.google.common.annotations.GwtCompatible;
import java.lang.annotation.Documented;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;

import java.time.Duration
import java.util.Arrays
import java.util.concurrent.BlockingQueue
import java.util.concurrent.CountDownLatch
import java.util.concurrent.Executors
import java.util.concurrent.LinkedBlockingQueue
import java.util.concurrent.SynchronousQueue
import java.util.concurrent.TimeUnit
import java.util.concurrent.TimeoutException
import java.util.concurrent.atomic.AtomicReference
import javax.net.ssl.SSLException

package org.codelibs.fess.filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.net.URLCodec;
import org.codelibs.core.lang.StringUtil;
import org.lastaflute.web.servlet.filter.LastaPrepareFilter;

    printEvent("callStart");
  }

  @Override public void callEnd(Call call) {
    printEvent("callEnd");
  }

  ...
}
```

We can use this listener to race a pair of concurrent HTTP requests:

```java
Request washingtonPostRequest = new Request.Builder()
    .url("https://www.washingtonpost.com/")
    .build();
client.newCall(washingtonPostRequest).enqueue(new Callback() {
  ...

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;
import org.jspecify.annotations.NullMarked;
import org.jspecify.annotations.Nullable;

/**
 * Tester to ensure forwarding wrapper works by delegating calls to the corresponding method with

 */

package com.google.common.collect;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.errorprone.annotations.CanIgnoreReturnValue;
import com.google.errorprone.annotations.concurrent.LazyInit;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Set;
import java.util.stream.Collector;

     */
    @ValidateTypeFailure
    public Long updatedTime;

    /**
     * The version number of the duplicate host configuration for optimistic locking.
     * This field is required to prevent concurrent modification conflicts
     * by ensuring the configuration hasn't been modified by another process.
     */
    @Required
    @ValidateTypeFailure
    public Integer versionNo;

import com.google.common.collect.HashMultiset;
import com.google.common.collect.ImmutableMap;
import com.google.common.collect.Multiset;
import com.google.errorprone.annotations.concurrent.LazyInit;
import java.lang.ref.Reference;
import java.lang.ref.SoftReference;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.Set;

     */
    @ValidateTypeFailure
    public Long updatedTime;

    /**
     * The version number of the data configuration for optimistic locking.
     * This field is required to prevent concurrent modification conflicts
     * by ensuring the configuration hasn't been modified by another process.
     */
    @Required
    @ValidateTypeFailure
    public Integer versionNo;

     */
    @ValidateTypeFailure
    public Long updatedTime;

    /**
     * The version number of the group for optimistic locking.
     * This field is required to prevent concurrent modification conflicts
     * by ensuring the group hasn't been modified by another process.
     */
    @Required
    @ValidateTypeFailure
    public Integer versionNo;