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

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

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