acidrain

Use Commons Codec from Apache Site
http://commons.apache.org/proper/commons-codec/

in package org.apache.commons.codec.binary
there is one class Base64

use static method :
* decodeBase64(byte[] base64Data)
* encodeBase64(byte[] binaryData)
* and be careful it works in array of bytes not String
* so beware of character encoding for Converting between your String to array of bytes.

Hopes this help you.

From your question:How can I know wether my server runs in safe mode or not?Did you mean php runs in safe mode or not ?You could check whether php runs in safe mode or notby phpinfo step above and find lines ctrl+f "safe_mode"

Here is quick step to learn java: (in my opinion)
* grab Sun j2sdk1.4.2 installation file
* grab Sun j2sdk1.4.2 doc
* prepare JEdit

Additional Hints
* forget about pointer, start using reference term
* keep in mind, passing primitive type (int, short, char, etc) as argument to a function (passing by value)
* and passing object as argument to a function (passing reference by value)
* mutable/imutable object decided whether there is get-setter method or not.
* learn the difference between deep copy and shallow copy from this link http://www.javaworld.com/
* java only support single inheritance in class level, but support muliple inheritance in interface level.
* visit http://www.informit.com/store/java-developers-almanac-1.4-volume-1-examples-and-quick-9780201752809 there is huge snippet code right there.
* learn GoF Gang of Four (optional)
* practice makes perfect

Hope this help you and still there is java information out there.