code: public void assertHasSize(@Nullable Description description, @Nullable String actual, int expectedSize) {
      assertNotNull(description, actual);
      int actualSize = actual.length();
      if (actualSize != expectedSize) {
        throw failures.failure(description, shouldHaveSize(actual, actualSize, expectedSize));
      }
    }
docs: Asserts that the size of the <em>actual</em> {@code String} is equal to the expected one.
  
  @param description the description of the <em>actual</em> {@code String}.
  @param actual the <em>actual</em> {@code String}.
  @param expectedSize the expected size of {@code actual}.
  @throws AssertionError if the <em>actual</em> {@code String} is {@code null}.
  @throws AssertionError if the size of the <em>actual</em> {@code String} is different than the expected one.