jjtree: 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/jjtree - from package: javacc

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

On Debian possible default full paths are:

/usr/bin/jjtree - from package: javacc

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

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