public void deposit(int acc,int Amount) {
    try {
        String host= "jdbc:derby://localhost:1527/ZaiLab";
        String uname= "siduduzo";
        String upass ="Password01";
        Connection con = DriverManager.getConnection( host, uname, upass );

        Statement stmt = con.createStatement( );

        if(Amount<1000) {
            JOptionPane.showMessageDialog( null,"Sorry! the Minimum you can deposit on a savings account is R1000");
        } else {
            try (PreparedStatement checkAccountExists = con.prepareStatement("SELECT 1 FROM SAVINGS WHERE ACCOUNTNUMBER = ?")) {
                checkAccountExists.setInt(1, acc);

                try (ResultSet RS = checkAccountExists.executeQuery()) {
                    int currentbal = RS.getInt("BALANCE");
                    int newbalance = currentbal+Amount;

                    if (RS.next()) {
                        String sql = "UPDATE SAVINGS WHERE ACCOUNTNUMBER =" +acc+ "SET BALANCE = "+newbalance;
                        stmt.executeUpdate(sql);
                        JOptionPane.showMessageDialog( null,"you have made a deposit to "+acc);
                    } else {
                        JOptionPane.showMessageDialog( null,"Invalid Account Number");
                    }
                }
            }
        }
    } catch ( SQLException err ) {
        System.out.println( err.getMessage( ) );
    }
}

try (PreparedStatement checkAccountExists = con.prepareStatement(
        "SELECT BALANCE FROM SAVINGS WHERE ACCOUNTNUMBER = ?")) {
     checkAccountExists.setInt(1, acc);

     try (ResultSet RS = checkAccountExists.executeQuery()) {
          if (RS.next()) {
              int currentbal = RS.getInt("BALANCE");
              int newbalance = currentbal + Amount;

              try (PreparedStatement stmt = con.prepareStatement(
                    "UPDATE SAVINGS SET BALANCE = ? WHERE ACCOUNTNUMBER = ?")){

                   stmt.setInt(1, newbalance);
                   stmt.setInt(2, acc);

                   stmt.executeUpdate();
                   JOptionPane.showMessageDialog(null, "you have made a deposit to "+acc);
              }

          } else {
              JOptionPane.showMessageDialog(null, "Invalid Account Number");
          }
     }
}

SELECT 1 FROM SAVINGS WHERE ACCOUNTNUMBER = ?

checkAccountExists.setInt(1, acc);

SELECT BALANCE FROM SAVINGS WHERE ACCOUNTNUMBER = ?

its change all the records in the column to the same record

sql = "SELECT * FROM department INNER JOIN employee ON department.depno=
employee.depno  ";
resultSet = statement.executeQuery(sql);

sql2="update employee set empage=? " ;
              ps=connection.prepareStatement(sql2);
while (resultSet.next()){
    empage=resultSet.getInt("empage");
     if(empage>50){  l= empage-3;
              //statement.executeUpdate(sql2);
         ps.setInt(1,l);
         ps.executeUpdate();
          ps.addBatch();
       }  }

    its change all the records in the column to the same record