//    (hypothetical) unsafe read by our caller. Note: adding 'volatile' does not fix this issue,
  //    it would just add an edge such that if done() observed non-null, then it would also
  //    definitely observe all earlier writes, but we still have no guarantee that done() would see
  //    the initial write (just stronger guarantees if it does).
  //
  // See: http://cs.oswego.edu/pipermail/concurrency-interest/2015-January/013800.html

  }

  /**
   * Returns the string if it is not null, or an empty string otherwise.
   *
   * @param string the string to test and possibly return
   * @return {@code string} if it is not null; {@code ""} otherwise
   */
  static String nullToEmpty(@CheckForNull String string) {
    return (string == null) ? "" : string;
  }

  /**
   * Returns the string if it is not empty, or a null string otherwise.
   *

          "cnn.ca",
          "ledger-enquirer.com",
          "it-trace.ch",
          "cool.dk",
          "cool.co.uk",
          "cool.de",
          "cool.es",
          "cool\uFF61fr", // Alternate dot character
          "cool.nl",
          "members.blah.nl.",
          "cool.se",
          "utenti.blah.it",
          "kt.co",
          "a\u7f51\u7edcA.\u7f51\u7edc.Cn" // "a网络A.网络.Cn"

    // way for it to return a false negative would be for the target value to jump around in the map
    // such that none of the subsequent iterations observed it, despite the fact that at every point
    // in time it was present somewhere int the map. This becomes increasingly unlikely as
    // CONTAINS_VALUE_RETRIES increases, though without locking it is theoretically possible.

              <version>0.6.1</version>
              <!-- TODO(cpovirk): In principle, it would make sense to *also* test compatibility with JDK 1.8, since guava-android also has JRE users. -->
            </signature>
            <ignores>
              <!-- Unsafe isn't part of the documented Android API, but it is available.
                   And in cases where it's not, we have fallbacks (except maybe Striped64 (b/307807965)?). -->

   *
   * <p>Many of the filtered collection's methods, such as {@code size()}, iterate across every
   * element in the underlying collection and determine which elements satisfy the filter. When a
   * live view is <i>not</i> needed, it may be faster to copy {@code Iterables.filter(unfiltered,
   * predicate)} and use the copy.
   *
   * <p><b>Warning:</b> {@code predicate} must be <i>consistent with equals</i>, as documented at

      Object value = new Object();
      map.put(key, value);
      originalMap.put(key, value);
      if (i >= maxSize) {
        Iterator<Object> it = originalMap.keySet().iterator();
        it.next();
        it.remove();
      }
      assertEquals(originalMap, map);
    }
  }

  public void testSegmentStoreComputedValue() {

      Object value = new Object();
      map.put(key, value);
      originalMap.put(key, value);
      if (i >= maxSize) {
        Iterator<Object> it = originalMap.keySet().iterator();
        it.next();
        it.remove();
      }
      assertEquals(originalMap, map);
    }
  }

  public void testSegmentStoreComputedValue() {

   * (used as the reference iterator) against a {@code PeekingIterator} that *wraps* such an
   * 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()}.
   */

}
```

## Links

-   [GitHub project](https://github.com/google/guava)
-   [Issue tracker: Report a defect or feature request](https://github.com/google/guava/issues/new)
-   [StackOverflow: Ask "how-to" and "why-didn't-it-work" questions](https://stackoverflow.com/questions/ask?tags=guava+java)
-   [guava-discuss: For open-ended questions and discussion](https://groups.google.com/group/guava-discuss)

## IMPORTANT WARNINGS