public CyclicIteration(NavigableMap<K, V> navigablemap, K startingkey) {
    if (navigablemap == null || navigablemap.isEmpty()) {
      this.navigablemap = null;
      this.tailmap = null;
    }
    else {
      this.navigablemap = navigablemap;
      this.tailmap = navigablemap.tailMap(startingkey, false); 
    }
  }
@Test
  public void testCyclicIteration() throws Exception {
    for(int n = 0; n < 5; n++) {
      checkCyclicIteration(n);
    }
  }