<s>
In	O
the	O
Java	B-Language
programming	I-Language
language	I-Language
,	O
heap	B-Language
pollution	I-Language
is	O
a	O
situation	O
that	O
arises	O
when	O
a	O
variable	O
of	O
a	O
parameterized	O
type	O
refers	O
to	O
an	O
object	O
that	O
is	O
not	O
of	O
that	O
parameterized	O
type	O
.	O
</s>
<s>
This	O
situation	O
is	O
normally	O
detected	O
during	O
compilation	B-Application
and	O
indicated	O
with	O
an	O
unchecked	O
warning	O
.	O
</s>
<s>
Later	O
,	O
during	O
runtime	B-Library
heap	B-Language
pollution	I-Language
will	O
often	O
cause	O
a	O
ClassCastException	O
.	O
</s>
<s>
A	O
source	O
of	O
heap	B-Language
pollution	I-Language
in	O
Java	B-Language
arises	O
from	O
the	O
fact	O
that	O
type	O
arguments	O
and	O
variables	O
are	O
not	O
reified	O
at	O
run-time	O
.	O
</s>
<s>
As	O
a	O
result	O
,	O
different	O
parameterized	O
types	O
are	O
implemented	O
by	O
the	O
same	O
class	O
or	O
interface	B-Language
at	O
run	B-Library
time	I-Library
.	O
</s>
<s>
All	O
invocations	O
of	O
a	O
given	O
generic	B-Language
type	O
declaration	O
share	O
a	O
single	O
run-time	O
implementation	O
.	O
</s>
<s>
This	O
results	O
in	O
the	O
possibility	O
of	O
heap	B-Language
pollution	I-Language
.	O
</s>
<s>
The	O
variable	O
will	O
always	O
refer	O
to	O
an	O
object	O
that	O
is	O
an	O
instance	O
of	O
a	O
class	O
that	O
implements	B-Language
the	O
parameterized	O
type	O
.	O
</s>
