Unexpected operator error

What is wrong in my code?

#!/bin/sh

LOOK_FOR="$1"

for i in `find $2 -name "*jar"`; do
  echo "Looking in $i ..."
  #jar tvf $i | grep $LOOK_FOR > /dev/null
  jar tvf "$i" | grep "$LOOK_FOR" 

  if [ $? == 0 ] ; then
    echo "==> Found \"$LOOK_FOR\" in $i"
  fi  
done #line 13

Output

wk@wk-laptop:$ sh lookjar.sh org/apache/axis/message/addressing/EndpointReference  /media/0C06E20B06E1F61C/uengine/uengine
Looking in /media/0C06E20B06E1F61C/uengine/uengine/defaultcompany/build/uengine_settings.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/defaultcompany/WebContent/uengine-web/lib/FCKeditor/WEB-INF/lib/commons-fileupload.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/defaultcompany/WebContent/uengine-web/lib/FCKeditor/WEB-INF/lib/FCKeditor-2.3.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/defaultcompany/WebContent/uengine-web/processmanager/signedmetaworks.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/hsqldb/lib/hsqldb.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/hsqldb/lib/servlet.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/src/lib/commons-discovery.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/src/lib/google.jar ...
[: 13: 1: unexpected operator
Looking in /media/0C06E20B06E1F61C/uengine/uengine/src/lib/jxl.jar ...