### Question:
IdGenerator { public final String newEntityId() { String id = Long.toString(getRandomEntityId() >>> 1, 16); int idLength = id.length(); if (idLength >= 16) { return id; } StringBuilder idWithPad = new StringBuilder(16); int padLength = 16 - idLength; char[] pad = RecyclableBuffers.chars(padLength); Arrays.fill(pad, 0, padLength, '0'); idWithPad.append(pad, 0, padLength); idWithPad.append(id); return idWithPad.toString(); }  abstract String newTraceId(); final String newEntityId();  }### Answer:
@Test public void testEntityIdPadding() { Assert.assertEquals("0000000000000123", new TestIdGenerator(0x123L).newEntityId()); Assert.assertEquals(Long.toString(Long.MAX_VALUE, 16), new TestIdGenerator(Long.MAX_VALUE).newEntityId()); }