Step by Step solution about How to resolve the algorithm Monads/Maybe monad step by step in the Java programming language

Java Monad Maybe Example

Overview: This Java code demonstrates the use of monads, specifically the Maybe monad, to handle optional values. Monads provide a way to represent and manipulate values that may or may not exist.

Code Breakdown:

1. Import Statement:

Imports the Optional class from the Java standard library, which represents optional values. An optional value can either contain a value or be empty (a "null" value).

2. main Method:

• System.out.println(doubler(5).flatMap(MonadMaybe::stringify).get()):
  • Calls the doubler method with the argument 5, which returns an Optional of the doubled value (10).
  • Calls the flatMap method on the Optional to apply the stringify method, which converts the doubled value into a string ("AA").
  • Gets the value from the transformed Optional using get().
• System.out.println(doubler(2).flatMap(MonadMaybe::stringifyNullable).get()):
  • Similar to the first line, but calls the stringifyNullable method, which returns an Optional of the stringified doubled value if it's greater than 0.
  • Because the doubled value in this case is 4, it gets stringified to "AAAA" and printed.
• Optional<String> option = doubler(0).flatMap(MonadMaybe::stringifyNullable);:
  • Calls the doubler method with 0, which returns an empty Optional (since 0 is not greater than 0).
  • Calls flatMap on the empty Optional to apply the stringifyNullable method, which returns an empty Optional since the condition is not met.
  • Assigns the empty Optional to the option variable.
• String result = option.isPresent() ? option.get() : "Result is Null";:
  • Checks if the option is present (not empty) using isPresent().
  • If present, gets the value using get(); otherwise, sets the result to "Result is Null".
• System.out.println(result);:
  • Prints the result variable, which will be "Result is Null" in this case because the option is empty.

3. doubler Method:

• private static Optional<Integer> doubler(int aN):
  • Accepts an integer aN and returns an Optional that contains double the value or is empty if aN is 0.

4. stringify Method:

• private static Optional<String> stringify(int aN):
  • Accepts an integer aN and returns an Optional that contains the string "A" repeated aN times or is empty if aN is 0.

5. stringifyNullable Method:

• private static Optional<String> stringifyNullable(int aN):
  • Accepts an integer aN and returns an Optional that contains the string "A" repeated aN times if aN is greater than 0 or is empty otherwise.

Explanation: This code demonstrates how to perform operations on optional values using monads. The Maybe monad represents the concept of an optional value that may or may not exist. The flatMap method allows us to apply a function to the value contained in an Optional, or to return an empty Optional if the original Optional is empty. This chaining of operations enables us to perform complex transformations on optional values in a concise and readable way.

import java.util.Optional;

public final class MonadMaybe {

	public static void main(String[] aArgs) {
	    System.out.println(doubler(5).flatMap(MonadMaybe::stringify).get());
	  
	    System.out.println(doubler(2).flatMap(MonadMaybe::stringifyNullable).get());
	    
	    Optional<String> option = doubler(0).flatMap(MonadMaybe::stringifyNullable);
	    
	    String result = option.isPresent() ? option.get() : "Result is Null";
	    
	    System.out.println(result);
	}
	
	private static Optional<Integer> doubler(int aN) {
		return Optional.of(2 * aN);
	}

	private static Optional<String> stringify(int aN) {
		return Optional.of("A".repeat(aN));
	}

	private static Optional<String> stringifyNullable(int aN) {
		return ( aN > 0 ) ? Optional.ofNullable("A".repeat(aN)) : Optional.ofNullable(null);
	} 

}