DocumentMatchers.java 文件源码

private static <T, U> Matcher<U> cast(Class<T> clazz, Matcher<? super T> downcastMatcher) {
    return new TypeSafeDiagnosingMatcher<U>() {
        @Override
        public void describeTo(Description description) {
            downcastMatcher.describeTo(description);
        }

        @Override
        protected boolean matchesSafely(Object item, Description mismatchDescription) {
            if (!clazz.isInstance(item)) {
                mismatchDescription.appendText("was a " + item.getClass().getSimpleName());
                return false;
            } if (downcastMatcher.matches(item)) {
                return true;
            } else {
                downcastMatcher.describeMismatch(item, mismatchDescription);
                return false;
            }
        }
    };
}