If you have a directory, for example /home/mhewedy/libs/jars/, this directory contains many jar/tar files, and you want to search the contents of these jar/tar files .

use this command :

cd /home/mhewedy/libs/jars/
for jar in *.jar; do echo “— $jar —” ; jar tf $jar | grep NullPointerException ; done;

Note, you may also use this command to search a list of tars for its contents:
for tar in *.tar; do echo “— $tar —” ; tar tf $tar | grep some_file_name ; done;