A common (reflexive, transitive) subtype of the erasures of
t2, if it exists.
If there is no such common subtype, then the two types are disjoint.
However, the converse is not true; for example, the parameterized types
Collection<String> are disjoint,
but their erasures (
do have common subtypes (such as
For the definition of the notion of erasure see JLS v8, section 4.6 (Type Erasure).