import static java.lang.annotation.RetentionPolicy.RUNTIME;

/**
 * Meta-annotation that marks other annotations as qualifier annotations.
 * <p>
 * Qualifiers are used to distinguish between multiple beans of the same type,
 * allowing for more precise control over which implementation should be injected.
 * Custom qualifier annotations should be annotated with {@code @Qualifier}.
 * <p>
 * Example of creating a custom qualifier:
 * <pre>

   * iterator (used as the target iterator).
   *
   * <p>This IteratorTester makes copies of the master so that it can later verify that {@link
   * PeekingIterator#remove()} removes the same elements as the reference's iterator {@code
   * remove()}.
   */
  private static class PeekingIteratorTester<T extends @Nullable Object> extends IteratorTester<T> {
    private final Iterable<T> master;

      HashFunction hasher = Hashing.goodFastHash(i);
      assertThat(hasher.bits()).isAtLeast(i);
      HashTestUtils.assertInvariants(hasher);
    }
  }

  // goodFastHash(32) uses Murmur3_32. Use the same epsilon bounds.
  public void testGoodFastHash32() {
    HashTestUtils.check2BitAvalanche(Hashing.goodFastHash(32), 250, 0.20);
    HashTestUtils.checkAvalanche(Hashing.goodFastHash(32), 250, 0.17);

as if it had a "vendor/" prefix. For example, within "crypto/tls",
an import of "golang.org/x/crypto/cryptobyte" resolves to
"vendor/golang.org/x/crypto/cryptobyte". When a package with the
same path is imported from a package outside std or cmd, it will
be resolved normally. Consequently, a binary may be built with two
copies of a package at different versions if the package is

  private final long totalLoadTime;

  private final long evictionCount;

  /**
   * Constructs a new {@code CacheStats} instance.
   *
   * <p>Five parameters of the same type in a row is a bad thing, but this class is not constructed
   * by end users and is too fine-grained for a builder.
   */
  @SuppressWarnings("GoodTime") // should accept a java.time.Duration
  public CacheStats(

  private final long totalLoadTime;

  private final long evictionCount;

  /**
   * Constructs a new {@code CacheStats} instance.
   *
   * <p>Five parameters of the same type in a row is a bad thing, but this class is not constructed
   * by end users and is too fine-grained for a builder.
   */
  @SuppressWarnings("GoodTime") // should accept a java.time.Duration
  public CacheStats(

    return new TreeMap<>();
  }

  /**
   * Creates a <i>mutable</i> {@code TreeMap} instance with the same mappings as the specified map
   * and using the same ordering as the specified map.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link
   * ImmutableSortedMap#copyOfSorted(SortedMap)} instead.
   *

    return new TreeMap<>();
  }

  /**
   * Creates a <i>mutable</i> {@code TreeMap} instance with the same mappings as the specified map
   * and using the same ordering as the specified map.
   *
   * <p><b>Note:</b> if mutability is not required, use {@link
   * ImmutableSortedMap#copyOfSorted(SortedMap)} instead.
   *

 * The cache stores its data in a directory on the filesystem. This directory must be exclusive to
 * the cache; the cache may delete or overwrite files from its directory. It is an error for
 * multiple processes to use the same cache directory at the same time.
 *
 * This cache limits the number of bytes that it will store on the filesystem. When the number of
 * stored bytes exceeds the limit, the cache will remove entries in the background until the limit

These examples are intentionally simple, but show how it all works.

In the chapters about security, there are utility functions that are implemented in this same way.

If you understood all this, you already know how those utility tools for security work underneath.

///