gjavah: 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/gjavah - from package: gcc-java

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

On Debian possible default full paths are:

/usr/bin/gjavah - from package: gcj-jdk

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

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