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Object Creation
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Singleton
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Ensures only one instance of a class exists and provides a global access point.
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Multiple instances may cause inconsistent shared state or unnecessary resource consumption.
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When one shared instance is required throughout the application.
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When independent instances or isolated state are required.
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Configuration management, logging, shared services.
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A Java configuration manager maintains one application-wide configuration instance.
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Object Creation
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Factory Method
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Defines an interface for creating objects while allowing subclasses or implementations to decide which object to create.
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Client code becomes tightly coupled to concrete classes.
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When object creation depends on runtime conditions.
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When object creation is simple and unlikely to change.
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Payment processing, notification services, file processing.
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A payment factory creates UPI, card, or net banking payment processors.
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Object Creation
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Abstract Factory
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Creates families of related objects without exposing their concrete implementations.
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Applications need compatible groups of objects without depending on implementation details.
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When multiple related product families are required.
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When only one simple object needs to be created.
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Multi-platform applications, database providers, UI frameworks.
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A banking application creates Oracle-specific or PostgreSQL-specific database components.
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Object Construction
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Builder
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Constructs complex objects step by step using a flexible construction process.
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Constructors with many parameters become difficult to maintain and understand.
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When objects have many optional or mandatory properties.
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When objects contain only a few simple properties.
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API request objects, configuration objects, report generation.
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A Java report builder creates customized financial reports with filters and formatting options.
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Object Cloning
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Prototype
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Creates new objects by copying an existing object.
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Creating complex objects repeatedly can be expensive.
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When object creation is costly and similar objects are required.
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When objects contain complex shared mutable references that cannot be safely copied.
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Document templates, configuration snapshots, workflow templates.
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A batch processing system clones a predefined job configuration for different business groups.
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