package com.sample.javaValidators;

import java.util.Optional;

public interface ValidationResult {

static ValidationResult valid() {

return ValidationSupport.valid();

}

static ValidationResult invalid(String reason) {

return new Invalid(reason);

}

boolean isValid();

Optional<String> getReason();

}

final class Invalid implements ValidationResult {

private final String reason;

Invalid(String reason){

this.reason = reason;

}

public boolean isValid(){

return false;

}

public Optional<String> getReason(){

return Optional.of(reason);

}

// equals and hashCode on field reason

}

final class ValidationSupport {

private static final ValidationResult valid = new ValidationResult(){

public boolean isValid(){ return true; }

public Optional<String> getReason(){ return Optional.empty(); }

};

static ValidationResult valid(){

return valid;

}

}