aj5: 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 Debian possible default full paths are:

/usr/bin/aj5 - from package: aspectj

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

Error in other languages:
aj5: bevel nie gevind nie
aj5: comandă negăsită
aj5: comando não encontrado
aj5: commande introuvable
aj5: command not found
aj5: käsku ei ole
aj5: không tìm thấy lệnh
aj5: komanda nerasta
aj5: Kommando nicht gefunden.
aj5: kommandot finns inte
aj5: komut yok
aj5: nie znaleziono polecenia
aj5: níor aimsíodh an t-ordú
aj5: no se encontró la orden
aj5: no s'ha trobat l'ordre
aj5: opdracht niet gevonden
aj5: parancs nem található
aj5: perintah tidak ditemukan
aj5: príkaz nenájdený
aj5: příkaz nenalezen
aj5: команда не найдена
aj5: командата не е открита
aj5: 命令找不到
aj5: コマンドが見つかりません