Java

14770

265

In which design pattern is the Comparator class used for comparing objects?

Junior — Middle

324

public class MoneyTransferService { /** * @param fromAccountId unique identifier of the user transferring funds * @param toAccountId unique identifier of the user receiving funds * @param amount transfer amount. Positive number */ @Transactional public void transferMoney(Long fromAccountId, Long toAccountId, BigDecimal amount) { if (amount.compareTo(BigDecimal.ZERO) <= 0) { throw new RuntimeException("Amount must be +"); } if (fromAccountId.equals(toAccountId)) { throw new RuntimeException("Account can't be the same"); } Long firstId = Math.min(fromAccountId, toAccountId); Long secondId = Math.max(fromAccountId, toAccountId); Account first = accountRepository.findByIdForUpdate(firstId) .orElseThrow(() -> new RuntimeException("Account not found")); Account second = accountRepository.findByIdForUpdate(secondId) .orElseThrow(() -> new RuntimeException("Account not found")); Account from = fromAccountId.equals(firstId) ? first : second; Account to = fromAccountId.equals(firstId) ? second : first; if (from.getBalance().compareTo(amount) < 0) { throw new RuntimeException("Balance is less 0"); } from.setBalance(from.getBalance().subtract(amount)); to.setBalance(from.getBalance().add(amount)); accountRepository.save(to); accountRepository.save(from); } } @Entity @Data public class Account { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) private Long id; private BigDecimal balance; }

Senior