Always! have your preconditions and Guard Clauses at the begging of the Method

Always! have your preconditions and Guard Clauses at the begging of the Method.

Don’t check Guard Clauses and don’t do validations in the middle of the method

DON’T

            if (CONTRACTED == newStatus) {
                newOffer.setContractedDate(now(of()));
                if (isCalculatedOffer(newOffer.getId())) {
                    newOffer = saveConsideringOldVersion(newOffer, oldOffer, companyId);
                    newOffer = recalculateContractedPrice(newOffer);
                } else {
                    throw new BadRequestAlertException(withKey(OFFER_NOT_CALCULATED));
                }
                facade.resetNewCustomerAndSubstitutionalSupplyFlags(newOffer.getCustomerId());
                facade.updateHasContractedOfferField(newOffer.getCustomerId(), true);
            }

DO it like this:

            if (CONTRACTED == newStatus) {
                if (!isCalculatedOffer(newOffer.getId())) {
                    throw new BadRequestAlertException(withKey(OFFER_NOT_CALCULATED));
                }
                newOffer.setContractedDate(now(of()));
                newOffer = saveConsideringOldVersion(newOffer, oldOffer, companyId);
                newOffer = recalculateContractedPrice(newOffer);

                facade.resetNewCustomerAndSubstitutionalSupplyFlags(newOffer.getCustomerId());
                facade.updateHasContractedOfferField(newOffer.getCustomerId(), true);
            } 

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Return Early Pattern

Preconditions, Postconditions, and Class Invariants