import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
public class BankTransfer {
   private static final String QUERY =
                "select * from Accounts where number = ?";
   private static final String UPDATE =
                "update Accounts set amount = ? where number = ?";
   public static void main(String[] args) throws Exception {
      try (Connection con = DriverManager.getConnection(
                              "jdbc:mysql://noelvaes.eu/StudentDB",
                              "student","student123");) {
         con.setAutoCommit(false);
         con.setTransactionIsolation(
                           Connection.TRANSACTION_REPEATABLE_READ);
         try (PreparedStatement qstmt =con.prepareStatement(QUERY);
PreparedStatement ustmt =con.prepareStatement(UPDATE);) {
setAmount(ustmt, 1, 100);
setAmount(ustmt, 2, 0);
double amount1 = 0;
double amount2 = 0;

while ((amount1 = getAmount(qstmt, 1)) > 0) {//tx start amount2 = getAmount(qstmt, 2);
setAmount(ustmt, 1, amount1 -= 1);
setAmount(ustmt, 2, amount2 += 1); System.out.println(amount1 + "\t" + amount2);
            con.commit();
         }
      } catch (Exception e) {
         System.out.println(e.getMessage());
         con.rollback();
} }
}
public static void setAmount(PreparedStatement ustmt,
//tx end
                                int number, double amount)
         throws SQLException {
      ustmt.setInt(2, number);
      ustmt.setDouble(1, amount);
      ustmt.executeUpdate();
   }
   public static double getAmount(PreparedStatement qstmt,
                                  int number) throws SQLException {
      double amount = 0;
      qstmt.setInt(1, number);
      try (ResultSet rs = qstmt.executeQuery()) {
         if (rs.next()) {
            amount = rs.getDouble("amount");
         }
}
      return amount;
   }
}