Class MixedJoin will return an
java.util.Iterator that will iterate over a given
Joiner and return tuples that represent a join as defined by the given boolean array.
So if joining three streams,
boolean []{true,false,false}} will result in a 'inner', 'outer', 'outer' join.
Joins perform based on the equality of the join keys. In the case of null values, Java treats two
null values as equivalent. SQL does not treat null values as equal. To produce SQL like results in a given
join, a new
java.util.Comparator will need to be used on the joined values to prevent null from
equaling null. As a convenience, see the
cascading.util.NullNotEquivalentComparator class.