@Override
    public int hashCode() {
        return Objects.hashCode(value);
    }
Returns the hash code value of the present value, if any, or 0 (zero) if
no value is present.

@return hash code value of the present value or 0 if no value is present
android/android_framework/base/src/main/java/github/tornaco/android/thanos/core/util/Optional.java