This book describes the principles of model building in financial engineering and explains those models as designs and working implementations for Java-based applications. The book provides software professionals with an accessible source of numerical methods or ready-to-use code for use in business applications. It is the first book to cover the topic of Java implementations for finance/investment applications and is written specifically to be accessible to software practitioners without prior accountancy/finance training. Throughout the book a series of packaged classes are developed to address a wide range of financial applications. The classes and methods are explained and designed in a way which allows the financial engineer complete flexibility. The classes can be used as off-the-shelf working solutions or the innovative developer can re-arrange and modify methods to create new products.