public class DataSource {

    private static DataSource     datasource;
    private BasicDataSource ds;

    private DataSource() throws IOException, SQLException, PropertyVetoException {
        ds = new BasicDataSource();
        ds.setDriverClassName("org.postgresql.Driver");
        ds.setUsername("postgres");
        ds.setPassword("postgres");
        ds.setUrl("jdbc:postgresql://localhost:5432/ehealth");

     // the settings below are optional -- dbcp can work with defaults
     //   ds.setMinIdle(5);
     //   ds.setMaxIdle(20);
     //   ds.setMaxOpenPreparedStatements(180);

    }

    public static DataSource getInstance() throws IOException, SQLException, PropertyVetoException {
        if (datasource == null) {
            datasource = new DataSource();
            return datasource;
        } else {
            return datasource;
        }
    }

    public Connection getConnection() throws SQLException {
        return this.ds.getConnection();
    }

}

public static Map<String, List<PreparedStatement>> test(int numberOfRequest) throws SQLException{
        try(Connection con = getHealthConnection(); Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                ResultSet.CONCUR_READ_ONLY,
                ResultSet.HOLD_CURSORS_OVER_COMMIT);){
            Map<String, List<PreparedStatement>> myMap = new HashMap<String, List<PreparedStatement>>();
            List<PreparedStatement> lstPreparedStmt = new ArrayList<PreparedStatement>();
            String request = "INSERT INTO PATIENT VALUES (?, ?, ?, ?, 'M', 'OTHER')";
            myMap.put(request, null);
            int counter = 0;
            String rqstSelect = "SELECT * FROM patient ORDER BY pat_id"; //initialize SELECT request
            ResultSet resRequest = stmt.executeQuery(rqstSelect); //execute SELECT
            String newId = createNewIdByIncrement(resRequest); //initialize first new id
            while(counter < numberOfRequest){
                String newName = generateRandomString(); //generate random new name
                String newLast = generateRandomString(); //generate random new last name
                String newLast2 = generateRandomString(); //generate random new last name 2
                PreparedStatement prep = con.prepareStatement(request, ResultSet.TYPE_SCROLL_INSENSITIVE,
                        ResultSet.CONCUR_READ_ONLY,
                        ResultSet.HOLD_CURSORS_OVER_COMMIT);
                prep.setString(1, newId);
                prep.setString(2, newName);
                prep.setString(3, newLast);
                prep.setString(4, newLast2);
                lstPreparedStmt.add(prep);
                counter = counter + 1; //increment counter
                int newIdAsInt = Integer.parseInt(newId) + 1; //increment id
                newId = concatenationZeroIntAsString(newIdAsInt, 8);
            }
            myMap.put(request, lstPreparedStmt);
            return myMap;
        }
    }

private void insertPreparedStatementRequest(int numberOfRequest) throws SQLException, IOException, PropertyVetoException{
        try(Connection con = DataSource.getInstance().getConnection(); Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE,
                ResultSet.CONCUR_READ_ONLY,
                ResultSet.HOLD_CURSORS_OVER_COMMIT);){
            // check number of row before insert
            String rqstCountRowBefore = "SELECT * FROM patient ORDER BY pat_id";
            ResultSet resCheckBefore = stmt.executeQuery(rqstCountRowBefore);
            int rowBefore = TestUtils.getRowCount(resCheckBefore);
            Assert.assertNotNull("Request's result is null", resCheckBefore);
            // insert X row
            Map<String, List<PreparedStatement>> allRequest = TestUtils.test(numberOfRequest);
            for(Map.Entry<String, List<PreparedStatement>> e : allRequest.entrySet()){
                List<PreparedStatement> lstStatement = e.getValue();
                Iterator<PreparedStatement> valIterator = lstStatement.iterator();
                while(valIterator.hasNext()){
                    valIterator.next().execute();
                }
            }
            // check number of row after insert
            String rqstCountrowAfter = "SELECT * FROM patient ORDER BY pat_id";
            ResultSet resCheckAfter = stmt.executeQuery(rqstCountrowAfter);
            int rowAfter = TestUtils.getRowCount(resCheckAfter);
            Assert.assertNotNull("Request's result is null", resCheckBefore);
            Assert.assertEquals("Insert result's request unsuccesfull", rowBefore + numberOfRequest, rowAfter);
        }
    }