### Question:
B2HeadersImpl implements B2Headers { @Override public String getValueOrNull(String name) { return pairs.get(name); } private  B2HeadersImpl(Map<String, String> pairs); @Override Collection<String> getNames(); @Override String getValueOrNull(String name); static Builder builder(); static Builder builder(B2Headers headersOrNull); @Override String toString();  }### Answer:
@Test public void testGetValueOrNull() { final B2Headers headers = makeNormal(); assertEquals("1234", headers.getValueOrNull(B2Headers.CONTENT_LENGTH)); assertNull(headers.getValueOrNull("noSuchHeader")); }