public static String truncateContent(String content) {
        if (content == null) {
            return "";
        } else if (content.length() <= SHOW_CONTENT_SIZE) {
            return content;
        } else {
            return content.substring(0, SHOW_CONTENT_SIZE) + "...";
        }
    }
@Test
    void testTruncateLongContent() {
        char[] arr = new char[101];
        Arrays.fill(arr, 'a');
        String content = new String(arr);
        String actual = ContentUtils.truncateContent(content);
        assertEquals(content.substring(0, 100) + "...", actual);
    }