*       class instead.
 *   <li>If checking an <i>impossible</i> condition (which <i>cannot</i> happen unless your own
 *       class or its <i>trusted</i> dependencies is badly broken), this is what ordinary Java
 *       assertions are for. Note that assertions are not enabled by default; they are essentially
 *       considered "compiled comments."

@Documented
@GwtCompatible
public @interface GwtIncompatible {
  /**
   * Describes why the annotated element is incompatible with GWT. Since this is generally due to a
   * dependence on a type/method which GWT doesn't support, it is sufficient to simply reference the
   * unsupported type/method. E.g. "Class.isInstance".
   *

 * <p>This interface is now a legacy type. Use {@code java.util.function.Function} (or the
 * appropriate primitive specialization such as {@code ToIntFunction}) instead whenever possible.
 * Otherwise, at least reduce <i>explicit</i> dependencies on this type by using lambda expressions
 * or method references instead of classes, leaving your code easier to migrate in the future.
 *

    cache.put(1, 10);
    cache.put(2, 20);
    cache.put(3, 30);
    cache.put(4, 40);
    cache.put(5, 50);

    assertEquals(null, cache.getIfPresent(10));
    // Order required to remove dependence on access order / write order constraint.
    assertEquals(Integer.valueOf(20), cache.getIfPresent(2));
    assertEquals(Integer.valueOf(30), cache.getIfPresent(3));
    assertEquals(Integer.valueOf(40), cache.getIfPresent(4));

    cache.put(1, 10);
    cache.put(2, 20);
    cache.put(3, 30);
    cache.put(4, 40);
    cache.put(5, 50);

    assertEquals(null, cache.getIfPresent(10));
    // Order required to remove dependence on access order / write order constraint.
    assertEquals(Integer.valueOf(20), cache.getIfPresent(2));
    assertEquals(Integer.valueOf(30), cache.getIfPresent(3));
    assertEquals(Integer.valueOf(40), cache.getIfPresent(4));