public boolean add(double element)
Ensures that I contain the specified element
(optional operation). Returns true
iff I changed as a result of this call.

If a collection refuses to add the specified
element for any reason other than that it already contains
the element, it must throw an exception (rather than
simply returning false). This preserves the invariant
that a collection always contains the specified element after
this call returns.

 public boolean addAll(DoubleCollection c)
 Adds  all of the elements in the
specified collection to me (optional operation).

 public  void clear()
Removes all my elements (optional operation).
I will be  empty  after this
method successfully returns.

 public boolean contains(double element)
Returns true iff I contain
the specified element.

 public boolean containsAll(DoubleCollection c)
Returns true iff I  contain 
all of the elements in the given collection.

 public boolean isEmpty()
Returns true iff I contain no elements.

 public DoubleIterator iterator()
Returns an iterator  over all my elements.
This base interface places no constraints on the order
in which the elements are returned by the returned iterator.

 public boolean removeAll(DoubleCollection c)
Removes all of my elements that are contained in the
specified collection (optional operation).
The behavior of this method is unspecified if
the given collection is modified while this method
is executing. Note that this includes the case
in which the given collection is this collection,
and it is not empty.

 public boolean removeElement(double element)
Removes a single occurrence of the specified element
(optional operation).

 public boolean retainAll(DoubleCollection c)
Removes all of my elements that are not contained in the
specified collection (optional operation).
(In other words, retains only my elements that are
contained in the specified collection.)
The behavior of this method is unspecified if
the given collection is modified while this method
is executing.

 public int size()
Returns the number of elements I contain.

 public double[] toArray()
Returns an array containing all of my elements.
The length of the returned array will be equal
to my  size .

The returned array will be independent of me,
so that callers may modify that
returned array without modifying this collection.

When I guarantee the order in which
elements are returned by an  iterator ,
the returned array will contain elements in the
same order.

 public double[] toArray(double[] a)
Returns an array containing all of my elements,
using the given array if it is large
enough. When the length of the given array is
larger than the number of elements I contain,
values outside of my range will be unchanged.

The returned array will be independent of me,
so that callers may modify that
returned array without modifying this collection.

When I guarantee the order in which
elements are returned by an  iterator ,
the returned array will contain elements in the
same order.