Does using the @FunctionalInterface annotation change the compilation process or the behavior of the code?

The @FunctionalInterface annotation in Java is used to explicitly indicate that an interface is intended to be a functional interface — meaning it contains exactly one abstract method. It does not directly alter the compilation process or the behavior of the code, but the compiler checks that the interface meets the requirements of a functional interface. If an interface annotated with this has more than one abstract method, compilation will fail with an error.

Example:

@FunctionalInterface
public interface MyFunction {
    void execute();
    // Adding a second abstract method here would cause a compilation error
}

Thus, @FunctionalInterface helps prevent errors when designing interfaces intended for lambda expressions and functional programming, but it does not affect program execution.