most JDBC drivers, ORM frameworks, and application servers implement their own connection pooling.
Why reinvent the wheel? Especially as it's far from a trivial endeavour.
You're unlikely to find a pdf on some website telling you all you need to know.
Think first of buying a good number of quality books on multithreading, concurrent computing, caching, memory management, design patterns, etc. etc. and actually understanding all they contain.

use some application server if u are dong ERP.
Those ones have standard mechanisms for conenction pooling.
Try looking through the javax.sql documentation for more help
Also try looking at the jdbc 3 specifications which are available for free from the sun java site
enjoy