@Test
  public void testGet() {
    CustomEntryConcurrentHashMap map = map5();
    assertEquals("A", map.get(one));
    CustomEntryConcurrentHashMap empty = new CustomEntryConcurrentHashMap();
    assertNull(map.get("anything"));
  }
get returns the correct element at the given key, or null if not present
geode-core/src/integrationTest/java/org/apache/geode/internal/util/concurrent/cm/ConcurrentHashMapJUnitTest.java