22.12. Custom Functional Interface Example

Try these first

1. 1.

   Define a functional interface with a method 'calculate'.

   Hint

   Use @FunctionalInterface annotation.

2. 2.

   What does a lambda expression enable you to do?

   Hint

   Think about how you might implement a new operation.

3. 3.

   What is a functional interface?

   • An interface with multiple abstract methods
   • An interface with exactly one abstract method
   • An interface with no methods

   Hint

   Remember the definition we covered.

4. 4.

   True or False: Lambda expressions can only call methods defined in the same class.

   • True
   • False

   Hint

   Think about the scope of lambda expressions.

5. 5.

   Create a functional interface 'Calculator' that can perform any mathematical operation such as addition, subtraction, multiplying, and division. Implement your interface using lambda expressions and test it with various operations.

   Hint

   Consider designing each operation as a separate lambda expression.

6. 6.

   Design an application that requires a functional interface to validate user input. Create a method that accepts a lambda for validation and uses it to check conditions like range and format.

   Hint

   Think about the common criteria for user inputs.