This is very useful when you need to:

* Have shared logic (the same code logic again and again).
* Share database connections.
* Enforce security, authentication, role requirements, etc.
* And many other things...

All these, while minimizing code repetition.

## First Steps { #first-steps }

Let's see a very simple example. It will be so simple that it is not very useful, for now.

 */
@SuppressSignatureCheck
class YubikeyClientAuth {
  fun run() {
    // The typical PKCS11 slot, may vary with different hardware.
    val slot = 0

    val config = "--name=OpenSC\nlibrary=/Library/OpenSC/lib/opensc-pkcs11.so\nslot=$slot\n"

    // May fail with ProviderException with root cause like
    // sun.security.pkcs11.wrapper.PKCS11Exception: CKR_SLOT_ID_INVALID

  /**
   * A sensible implementation of {@link NavigableSet#descendingSet} in terms of the other methods
   * of {@link NavigableSet}, notably including {@link NavigableSet#descendingIterator}.
   *
   * <p>In many cases, you may wish to override {@link ForwardingNavigableSet#descendingSet} to
   * forward to this implementation or a subclass thereof.
   *
   * @since 12.0
   */

/*
 * Copyright (C) 2011 The Guava Authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
 * in compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License

/*
 * Copyright (C) 2014 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

    String[] WINERR_MESSAGES = { "The operation completed successfully.", "Access is denied.",
            "No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept.",
            "The pipe state is invalid.", "All pipe instances are busy.", "The pipe is being closed.",

    String[] WINERR_MESSAGES = { "The operation completed successfully.", "Access is denied.",
            "No more connections can be made to this remote computer at this time because there are already as many connections as the computer can accept.",
            "The pipe state is invalid.", "All pipe instances are busy.", "The pipe is being closed.",
            "No process is on the other end of the pipe.", "More data is available.",

		}
	}
}

// encodeMarker will encode a uuid and return it as a marker.
// uuid cannot contain '[', ':' or ','.
func (o listPathOptions) encodeMarker(marker string) string {
	if o.ID == "" {
		// Mark as returning listing...
		return fmt.Sprintf("%s[minio_cache:%s,return:]", marker, markerTagVersion)
	}
	if strings.ContainsAny(o.ID, "[:,") {

   */
  public CharMatcher or(CharMatcher other) {
    return new Or(this, other);
  }

  /**
   * Returns a {@code char} matcher functionally equivalent to this one, but which may be faster to
   * query than the original; your mileage may vary. Precomputation takes time and requires more
   * memory, so it is only likely to be worthwhile if the precomputed matcher is queried very often.
   *

  /**
   * A sensible implementation of {@link NavigableSet#descendingSet} in terms of the other methods
   * of {@link NavigableSet}, notably including {@link NavigableSet#descendingIterator}.
   *
   * <p>In many cases, you may wish to override {@link ForwardingNavigableSet#descendingSet} to
   * forward to this implementation or a subclass thereof.
   *
   * @since 12.0
   */