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Design patterns are typical solutions to commonly occurring problems in software design. You can’t just find a pattern and copy it into your program, the way you can with off-the-shelf functions or libraries. The pattern is not a specific piece of code, but a general concept for solving a particular problem. They are like pre-made blueprints that you can customize to solve a recurring design problem in your code.

The book Dive Into Design Patterns illustrates 22 classic design patterns and 8 design principles that these patterns are based on.

- Every chapter starts from a discussion of a real life software design problem which is then progressively solved by applying one of the patterns.
- Then goes a detailed review of the pattern’s structure and its variations, followed by a code example.
- Then the books shows various applications of the pattern and teaches how to implement the pattern step by step, even in an existing program.
- Each chapter concludes with a discussion of pros and cons of the pattern and its relations, similarities and differences with other patterns.