a.java

public static <T> Validator<T extends Comparable<T>> positiveValidator(T zeroValue) {
    return value -> {
        if (zeroValue.compareTo(value) < 0) {
             return Optional.empty()
        }
        else {
             rerurn Optional.of(String.format("Value must be positive but was '%s'", value));
        };
}
  
public static Validator<Integer> positiveValidator() {
    return positiveValidator(0);
}
  
public static Validator<Long> positiveValidator() {
    return positiveValidator(0L);
}


// VS
  
 public static Validator<Long> positive() {
        return value -> {
            if (value > 0) {
                return Optional.empty();
            }
            return Optional.of("Value should be positive but was " + value);
        };
}
  
public static Validator<Integer> positive() {
        return value -> {
            if (value > 0) {
                return Optional.empty();
            }
            return Optional.of("Value should be positive but was " + value);
        };
}