public static String underlineToCamel(String param) {
        return formatCamel(param, UNDERLINE);
    }
@Test
    void underlineToCamel() {
        assertThat(StringFormatUtils.underlineToCamel(null)).isEqualTo("");
        assertThat(StringFormatUtils.underlineToCamel("  ")).isEqualTo("");
        assertThat(StringFormatUtils.underlineToCamel("abc_def_gh")).isEqualTo("abcDefGh");
    }