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## Common Design Pattern Application Scenarios Let's quickly understand the application scenarios of several commonly used design patterns through a table: | Design Pattern | Problem Solved | Typical Application Scenarios | | --- | --- | --- | | Singleton Pattern | Ensures globally unique instance | Database connections, configuration management, logging systems | | Factory Pattern | Complex object creation logic | Creating different types of objects based on different conditions | | Observer Pattern | Dynamic notification between objects | Event handling systems, message subscription | | Decorator Pattern | Dynamically extending functionality | IO stream processing, middleware chains |