<s>
Javassist	B-Language
(	O
Java	B-Language
programming	I-Language
assistant	O
)	O
is	O
a	O
Java	B-Language
library	B-Library
providing	O
a	O
means	O
to	O
manipulate	O
the	O
Java	B-Language
bytecode	I-Language
of	O
an	O
application	O
.	O
</s>
<s>
In	O
this	O
sense	O
Javassist	B-Language
provides	O
the	O
support	O
for	O
structural	O
reflection	B-Language
,	O
i.e.	O
</s>
<s>
the	O
ability	O
to	O
change	O
the	O
implementation	O
of	O
a	O
class	O
at	O
run	B-Library
time	I-Library
.	O
</s>
<s>
Bytecode	O
manipulation	O
is	O
performed	O
at	O
load-time	B-Operating_System
through	O
a	O
provided	O
class	B-Language
loader	I-Language
.	O
</s>
<s>
Javassist	B-Language
enables	O
Java	B-Language
programs	O
to	O
define	O
a	O
new	O
class	O
at	B-Library
runtime	I-Library
and	O
to	O
modify	O
a	O
class	O
file	O
when	O
the	O
JVM	O
loads	O
it	O
.	O
</s>
<s>
Unlike	O
other	O
similar	O
bytecode	O
editors	O
,	O
Javassist	B-Language
provides	O
two	O
levels	O
of	O
API	O
:	O
source	O
level	O
and	O
bytecode	O
level	O
.	O
</s>
<s>
Using	O
the	O
source-level	O
API	O
,	O
programmers	O
can	O
edit	O
a	O
class	O
file	O
without	O
knowledge	O
of	O
the	O
specifications	O
of	O
the	O
Java	B-Language
bytecode	I-Language
;	O
the	O
whole	O
API	O
is	O
designed	O
with	O
only	O
the	O
vocabulary	O
of	O
the	O
Java	B-Language
language	I-Language
.	O
</s>
<s>
Programmers	O
can	O
even	O
specify	O
inserted	O
bytecode	O
in	O
the	O
form	O
of	O
Java	B-Language
source	O
text	O
;	O
Javassist	B-Language
compiles	O
it	O
on	O
the	O
fly	O
.	O
</s>
<s>
Javassist	B-Language
can	O
be	O
used	O
for	O
the	O
following	O
:	O
</s>
