Best Practices and Design Patterns

Best Practices for Writing Lambdas:

1. Keep Lambdas Short and Readable:

   • Lambdas should be concise and focused on a specific task for readability.

2. Avoid Side Effects:

   • Lambdas should not modify external state. They should be stateless and operate only on their input parameters.

3. Use Existing Functional Interfaces:

   • Whenever possible, use existing functional interfaces from the java.util.function package instead of creating custom interfaces.

4. Be Mindful of Exception Handling:

   • Be cautious when handling exceptions within lambdas. Consider wrapping checked exceptions or using functional interfaces that declare exceptions.

5. Consider Parallelism:

   • When using parallel streams, ensure that the operations inside the lambda are thread-safe.

6. Immutable Data:

   • Prefer using immutable data inside lambdas to avoid unintended side effects.

Lambda Design Patterns:

1. Strategy Pattern with Lambdas:

   Example of Strategy Pattern with Lambdas:

   import java.util.List;
   import java.util.function.Predicate;
   
   class Filter {
       public static <T> List<T> filter(List<T> items, Predicate<T> predicate) {
           return items.stream().filter(predicate).toList();
       }
   }
   
   public class StrategyPatternExample {
       public static void main(String[] args) {
           List<String> names = List.of("Alice", "Bob", "Charlie", "David");
   
           // Using lambda expression as a strategy
           List<String> filteredNames = Filter.filter(names, name -> name.length() > 4);
           System.out.println("Filtered Names: " + filteredNames); // Output: Filtered Names: [Alice, Charlie]
       }
   }

2. Command Pattern with Lambdas:

   Example of Command Pattern with Lambdas:

   interface Command {
       void execute();
   }
   
   class Light {
       void turnOn() {
           System.out.println("Light is ON");
       }
   
       void turnOff() {
           System.out.println("Light is OFF");
       }
   }
   
   public class CommandPatternExample {
       public static void main(String[] args) {
           Light light = new Light();
   
           // Using lambdas as commands
           Command turnOnCommand = light::turnOn;
           Command turnOffCommand = light::turnOff;
   
           // Invoking commands
           turnOnCommand.execute(); // Output: Light is ON
           turnOffCommand.execute(); // Output: Light is OFF
       }
   }

In the Strategy Pattern, a lambda expression is used as a strategy to filter a list of names. In the Command Pattern, lambdas are used as commands to control the state of a Light object.

By following best practices and utilizing design patterns, you can write clean, readable, and maintainable code with lambdas in Java. These practices and patterns enhance the flexibility and expressiveness of your functional programming approach.