diff-jars: 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/diff-jars - from package: jpackage-utils

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

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