javac: 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/lib/jvm/java-1.5.0-gcj-4.8-amd64/bin/javac - from package: gcj-4.8-jdk
/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/bin/javac - from package: gcj-4.9-jdk
/usr/lib/debug/usr/lib/jvm/java-7-openjdk-amd64/bin/javac - from package: openjdk-7-dbg
/usr/lib/jvm/java-7-openjdk-amd64/bin/javac - from package: openjdk-7-jdk

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

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