Factory Pattern

interface Shape {
  void draw();
}

class ShapeFactory {
  public Shape getShape(String type) {
    if(type.equals("circle")) return new Circle();
    if(type.equals("square")) return new Square();
    return null;
  }
}

// Step 1: Create interface
interface Shape {
  void draw();
}

// Step 2: Implement classes
class Circle implements Shape {
  public void draw() {
    System.out.println("Drawing Circle");
  }
}

class Square implements Shape {
  public void draw() {
    System.out.println("Drawing Square");
  }
}

// Step 3: Factory class
class ShapeFactory {

  public Shape getShape(String type) {

    if (type == null) return null;

    if (type.equalsIgnoreCase("circle")) {
      return new Circle();
    } else if (type.equalsIgnoreCase("square")) {
      return new Square();
    }

    return null;
  }
}

// Step 4: Main class
public class Main {

  public static void main(String[] args) {

    ShapeFactory factory = new ShapeFactory();

    Shape s1 = factory.getShape("circle");
    s1.draw();

    Shape s2 = factory.getShape("square");
    s2.draw();

  }
}

// Output:
// Drawing Circle
// Drawing Square

• 1 A creational design pattern.
• 2 Creates objects without exposing logic.
• 3 Uses a common interface.
• 4 Delegates object creation.

• 1 Simple Factory.
• 2 Factory Method Pattern.
• 3 Abstract Factory Pattern.

• 1 Reduces tight coupling.
• 2 Improves code flexibility.
• 3 Centralizes object creation.
• 4 Makes code scalable.

• 1 Spring Framework bean creation.
• 2 Database driver loading.
• 3 UI component creation.
• 4 Logging frameworks.

• 1 Used in Spring Bean creation.
• 2 Used in JDBC driver management.
• 3 Used in UI component creation.
• 4 Used in logging framework instantiation.
• 5 SaaS products use Factory Design Pattern in Java in services, dashboards, background jobs, and API workflows.
• 6 ERP and banking systems apply Factory Design Pattern in Java with validation, logging, review, and rollback plans.
• 7 E-commerce and healthcare platforms use Factory Design Pattern in Java carefully because reliability and data correctness matter.

• 1 A Java program first evaluates the surrounding context, then applies the Factory Design Pattern in Java rules to the current data.
• 2 The important mental model is input, transformation, result, and failure path.
• 3 In production, the same flow usually sits inside a larger layer such as a controller, service, repository, job, or UI component.

• 1 Choose the simplest implementation first, then measure real workloads.
• 2 Watch for repeated work inside loops, unnecessary allocations, and slow I/O in hot paths.
• 3 Prefer clear data structures and stable APIs before micro-optimizing syntax.

• 1 Treat external input as untrusted until it is validated.
• 2 Avoid hardcoded secrets and never print sensitive values in examples or logs.
• 3 Use established libraries for authentication, encryption, parsing, and database access.

• 1 Overusing factory for simple object creation.
• 2 Creating too many factory classes.
• 3 Violating Open/Closed principle if not designed well.
• 4 Tight coupling inside factory logic.
• 5 Skipping the small working example before adding framework code.
• 6 Ignoring null, empty, duplicate, and boundary inputs.
• 7 Mixing business logic, input handling, and output formatting in one place.
• 8 Using broad error handling that hides the real failure.
• 9 Forgetting to test the behavior after refactoring.
• 10 Adding clever code that future maintainers will struggle to read.

• 1 Use factory when object creation is complex.
• 2 Follow Open/Closed principle.
• 3 Keep factory logic centralized.
• 4 Use interfaces for flexibility.
• 5 Start with clear requirements and one minimal working example.
• 6 Use meaningful names that explain business intent.
• 7 Keep examples small enough to debug line by line.
• 8 Validate input at every trust boundary.
• 9 Handle errors explicitly and preserve useful context.
• 10 Prefer simple control flow over deeply nested logic.
• 11 Separate domain logic from I/O and framework code.
• 12 Write tests for normal, boundary, and failure cases.
• 13 Review security assumptions before production use.
• 14 Measure performance before optimizing.
• 15 Document non-obvious decisions close to the code or in project notes.
• 16 Use official documentation when behavior is version-specific.
• 17 Keep dependencies current and remove unused code.
• 18 Avoid hardcoded secrets, credentials, and environment-specific paths.
• 19 Log operational events without exposing sensitive data.
• 20 Design examples so learners can safely modify and rerun them.

• 1 Beginner: rewrite the example with different names and values.
• 2 Intermediate: add validation and handle one expected failure case.
• 3 Advanced: place Factory Design Pattern in Java inside a small service-style design with tests.

• 1 Build a small Java console feature that demonstrates Factory Design Pattern in Java.
• 2 Accept input, process it with the concept, print a clear result, and handle invalid input.
• 3 Add a README note explaining the design choice and two edge cases you tested.

• 1 If the program does not compile, check spelling, imports, braces, and file/class names first.
• 2 If output is unexpected, print intermediate values and verify each branch of the logic.
• 3 If the design feels complex, reduce it to the smallest working example and add pieces back one at a time.

• 1 Practice Factory Design Pattern in Java with a second example from a business domain such as inventory, payroll, banking, or e-commerce.
• 2 Review related Java topics that cover data flow, error handling, testing, and clean design.
• 3 Compare your solution with official documentation and simplify anything you cannot explain clearly.