Returns <tt>true</tt> if this map maps one or more keys to the
specified value. More formally, returns <tt>true</tt> if and only if
this map contains at least one mapping to a value <tt>v</tt> such that
<tt>(value==null ? v==null : value.equals(v))</tt>. This operation
will probably require time linear in the map size for most
implementations of the <tt>Map</tt> interface.
@param value value whose presence in this map is to be tested
@return <tt>true</tt> if this map maps one or more keys to the
specified value
@throws ClassCastException if the value is of an inappropriate type for
this map
(<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
@throws NullPointerException if the specified value is null and this
map does not permit null values
(<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)
Returns <tt>true</tt> if this map maps one or more keys to the specified value. More formally, returns <tt>true</tt> if and only if this map contains at least one mapping to a value <tt>v</tt> such that <tt>(value==null ? v==null : value.equals(v))</tt>. This operation will probably require time linear in the map size for most implementations of the <tt>Map</tt> interface.
@param value value whose presence in this map is to be tested @return <tt>true</tt> if this map maps one or more keys to the specified value @throws ClassCastException if the value is of an inappropriate type for this map (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>) @throws NullPointerException if the specified value is null and this map does not permit null values (<a href="{@docRoot}/java/util/Collection.html#optional-restrictions">optional</a>)