FULL PRODUCT VERSION :
java version "1.6.0_20"
Java(TM) SE Runtime Environment (build 1.6.0_20-b02)
Java HotSpot(TM) Client VM (build 16.3-b01, mixed mode, sharing)

ADDITIONAL OS VERSION INFORMATION :
Microsoft Windows [Version 6.1.7600]

A DESCRIPTION OF THE PROBLEM :
jarsigner tool remove the entries from "MAINFEST.MF" file before adding signing information on same file.

Signed jar's "MAINFEST.MF" will lose previous information.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
1. Creating a jar with mainfest file. Cross check that this mainfest contain information about jar.
2. Use jarsigner tool to sign this jar.
3. Check mainfest of signed jar.  Mainfest of this jar will has signed classed information but previous information has been deleted.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Jarsigner should not delete data form mainfest.
ACTUAL -
jarsinger tool remove the information from mainfest of jar before adding the class signing information in same file.

REPRODUCIBILITY :
This bug can be reproduced always.