thumbelina: 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/share/doc/libhtmlparser-java-doc/examples/bin/thumbelina - from package: libhtmlparser-java-doc

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

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