Java Design Patterns Learning Path

Design patterns are reusable solutions to common software design problems.

This page is the home article for the Java Design Patterns section. Use it as the ordered table of contents for the complete series.

The series is grouped into the three classic design pattern families:

• Creational patterns: how objects are created.
• Structural patterns: how classes and objects are composed.
• Behavioral patterns: how objects communicate and distribute responsibility.

The order below also controls the Previous and Next navigation at the bottom of each article in this folder.

Complete Pattern Order

Creational Patterns

Creational patterns help you create objects in a flexible, controlled, and maintainable way.

No	Pattern	Use When
01	Singleton Design Pattern in Java	You need exactly one shared instance, such as configuration, registry, or application-level service
02	Factory Method Design Pattern in Java	You want subclasses or factory methods to decide which object implementation to create
03	Abstract Factory Design Pattern in Java	You need to create families of related objects without depending on concrete classes
04	Builder Design Pattern in Java	You need to build complex objects step by step with readable construction code
05	Prototype Design Pattern in Java	You want to create new objects by copying an existing object

Structural Patterns

Structural patterns help you compose classes and objects into larger, cleaner designs.

No	Pattern	Use When
06	Adapter Design Pattern in Java	You need to make incompatible APIs work together
07	Bridge Design Pattern in Java	You want to separate abstraction from implementation so both can evolve independently
08	Composite Design Pattern in Java	You need to treat individual objects and groups of objects uniformly
09	Decorator Design Pattern in Java	You want to add behavior dynamically without changing the original class
10	Facade Design Pattern in Java	You want to provide a simple interface over a complex subsystem
11	Flyweight Design Pattern in Java	You need to reduce memory usage by sharing common object state
12	Proxy Design Pattern in Java	You need controlled access to another object, such as lazy loading, security, caching, or remote access

Behavioral Patterns

Behavioral patterns help objects communicate, coordinate, and assign responsibilities.

No	Pattern	Use When
13	Chain of Responsibility Design Pattern in Java	You want a request to pass through a chain of handlers
14	Command Design Pattern in Java	You want to encapsulate an action as an object for queues, undo, retries, or audit
15	Interpreter Design Pattern in Java	You need to interpret a small language, rule syntax, or expression grammar
16	Iterator Design Pattern in Java	You need to access collection elements without exposing internal structure
17	Mediator Design Pattern in Java	You want objects to communicate through a central coordinator instead of directly
18	Memento Design Pattern in Java	You need to capture and restore object state, such as undo or snapshots
19	Observer Design Pattern in Java	You want dependent objects to react when another object changes state
20	State Design Pattern in Java	You want an object to change behavior based on its internal state
21	Strategy Design Pattern in Java	You need interchangeable algorithms behind a common interface
22	Template Method Design Pattern in Java	You want a base class to define an algorithm skeleton while subclasses customize steps
23	Visitor Design Pattern in Java	You want to add operations to object structures without modifying those structures

Recommended Learning Flow

flowchart TD
    A["Creational Patterns"] --> A1["01 Singleton"]
    A1 --> A2["02 Factory Method"]
    A2 --> A3["03 Abstract Factory"]
    A3 --> A4["04 Builder"]
    A4 --> A5["05 Prototype"]

    A5 --> B["Structural Patterns"]
    B --> B1["06 Adapter"]
    B1 --> B2["07 Bridge"]
    B2 --> B3["08 Composite"]
    B3 --> B4["09 Decorator"]
    B4 --> B5["10 Facade"]
    B5 --> B6["11 Flyweight"]
    B6 --> B7["12 Proxy"]

    B7 --> C["Behavioral Patterns"]
    C --> C1["13 Chain of Responsibility"]
    C1 --> C2["14 Command"]
    C2 --> C3["15 Interpreter"]
    C3 --> C4["16 Iterator"]
    C4 --> C5["17 Mediator"]
    C5 --> C6["18 Memento"]
    C6 --> C7["19 Observer"]
    C7 --> C8["20 State"]
    C8 --> C9["21 Strategy"]
    C9 --> C10["22 Template Method"]
    C10 --> C11["23 Visitor"]

How to Study This Series

If you are new to design patterns, follow the numeric order from 01 to 23.

If you are preparing for interviews:

• Learn Creational patterns first because they are common in object creation questions.
• Learn Structural patterns next because they appear often in framework and API design.
• Learn Behavioral patterns last because they are heavily used in workflow, event-driven, and enterprise systems.

Each article explains the pattern intent, real-world use cases, Java implementation, Spring usage, pros and cons, and interview notes.