code: public void assertHasSize(Description description, List<?> actual, int expectedSize) {
      assertNotNull(description, actual);
      int sizeOfActual = actual.size();
      if (sizeOfActual != expectedSize) {
        throw failures.failure(description, shouldHaveSize(actual, sizeOfActual, expectedSize));
      }
    }
docs: Asserts that the number of elements in the given {@code List} is equal to the expected one.
  
  @param description  contains information about the assertion.
  @param actual       the given {@code List}.
  @param expectedSize the expected size of {@code actual}.
  @throws AssertionError if the given {@code Collection} is {@code null}.
  @throws AssertionError if the number of elements in the given {@code List} is different than the expected one.