Patterns have emerged as one of the most significant new fields in object-oriented technology. Patterns allow experienced programmers to share patterns or nuggets of lessons learned with other programmers to help save enormous amounts of product development time and money. Patterns can be a segment of Java code that can be reused, best design practices for developing a database in Java, or project management and people skills that work time and time again for a project. Many programmers and developers want to take advantage of patterns, but don't have the time or experience to document them for their organizations. The documentation of these patterns along with practical examples has made books in this area sell so well. Patterns are usually grouped together based on the phase that they occur in a project's life cycle. There are five main stages of the software development life cycle: Requirements and Business Modeling - determine what the business needs are. Analysis - define the parameters and scope of the project. Design - begin the work on the project. Implementation - roll out the project. Testing - refine and improve the program/system. The most popular group of patternsDesign Patternsoccur in the Analysis and Design phases of the life cycle.