You want to use Commons Codec.

To use Commons Codec in a Maven 2 project, add the following dependency to your project's pom.xml:

<dependency>
  <groupId>commons-codec</groupId>
  <artifactId>commons-codec</artifactId>
  <version>1.3</version>
</dependency>  

If you are not sure what this means, I'd suggest reading Maven: The Definitive Guide. When you depend on a library in Maven 2, all you need to do is add the dependency groupId, artifactId, and version to your project's dependencies. Once you do this, Maven 2 will download the dependency and make it available on your project's classpath.

The Commons Codec library is a small library, which includes encoders and decoders for common encoding algorithms, such as Hex, Base64; and phonetic encoders, such as Metaphone, DoubleMetaphone, and Soundex. This tiny component was created to provide a definitive implementation of Base64 and Hex, encouraging reuse and reducing the amount of code duplication between various Apache projects.

To learn more about Commons Codec, visit the Commons Codec project at http://commons.apache.org/codec/.