DemoApp.java

package com.bobocode;

import com.bobocode.pool.PooledDataSource;
import lombok.SneakyThrows;

import javax.sql.DataSource;
import java.sql.SQLException;

public class DemoApp {
    @SneakyThrows
    public static void main(String[] args) {
        var dataSource = initializePooledDataSource();
        var total = 0.0;
        var start = System.nanoTime();
        for (int i = 0; i < 500; i++) {
            try (var connection = dataSource.getConnection()) {
                connection.setAutoCommit(false);
                try (var statement = connection.createStatement()) {
                    var rs = statement.executeQuery("select random() from products");
                    rs.next();
                    total += rs.getDouble(1);
                }
                connection.rollback();
            }
        }
        System.out.println((System.nanoTime() - start) / 1000_000 + " ms");
        System.out.println(total);
    }

    private static DataSource initializePooledDataSource() throws SQLException, InterruptedException {
        return new PooledDataSource("jdbc:postgresql://localhost:5432/postgres",
                "postgres",
                "root");
    }
}