grepjar: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/grepjar - from package: libgcj

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/grepjar - from package: fastjar

You may install the required package with command apt-get install {package}

Error in other languages:
grepjar: bevel nie gevind nie
grepjar: comandă negăsită
grepjar: comando não encontrado
grepjar: commande introuvable
grepjar: command not found
grepjar: käsku ei ole
grepjar: không tìm thấy lệnh
grepjar: komanda nerasta
grepjar: Kommando nicht gefunden.
grepjar: kommandot finns inte
grepjar: komut yok
grepjar: nie znaleziono polecenia
grepjar: níor aimsíodh an t-ordú
grepjar: no se encontró la orden
grepjar: no s'ha trobat l'ordre
grepjar: opdracht niet gevonden
grepjar: parancs nem található
grepjar: perintah tidak ditemukan
grepjar: príkaz nenájdený
grepjar: příkaz nenalezen
grepjar: команда не найдена
grepjar: командата не е открита
grepjar: 命令找不到
grepjar: コマンドが見つかりません