### Question:
NumberFormatAtomicSignID implements SignIDProvider { @Override public String incrementAndGet() { int newSignID = provider.incrementAndGet(); return String.format("%03d", newSignID); } NumberFormatAtomicSignID();  NumberFormatAtomicSignID(String maxSignID); @Override void setCurrentMaxSignId(String maxSignId); @Override String incrementAndGet(); @Override String get(); @Override int parse(String id);  }### Answer:
@Test void incrementAndGet() { NumberFormatAtomicSignID val = new NumberFormatAtomicSignID(); String actual = val.incrementAndGet(); assertEquals("001", actual); }