매번 헷갈리는 문자열 길이

String s = "한글1"; assertEquals(3, s.length()); assertEquals("한", s.substring(0, 1)); assertEquals("한글", s.substring(0, 2)); assertEquals("글1", s.substring(1, 3)); assertEquals(s, s.substring(0, s.length())); byte[] b = s.getBytes(); assertEquals(5, b.length); assertEquals("한", new String(b, 0, 2)); assertEquals("한글", new String(b, 0, 4)); assertEquals("글1", new String(b, 2, 3)); assertEquals(s, new String(b, 0, b.length));