alreadyCalledEndOfData = true;
            return endOfData();
          }
        };

    try {
      empty.peek();
      fail("peek() should throw NoSuchElementException at end");
    } catch (NoSuchElementException expected) {
    }

    try {
      empty.peek();
      fail("peek() should continue to throw NoSuchElementException at end");
    } catch (NoSuchElementException expected) {
    }

            alreadyCalledEndOfData = true;
            return endOfData();
          }
        };

    try {
      empty.peek();
      fail("peek() should throw NoSuchElementException at end");
    } catch (NoSuchElementException expected) {
    }

    try {
      empty.peek();
      fail("peek() should continue to throw NoSuchElementException at end");
    } catch (NoSuchElementException expected) {
    }