Java连接PostgreSQL数据库测试

import java.sql.DriverManager;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.ResultSet;
import java.sql.Statement;

public class PG {
    public static void main(String[] args) {
        System.out.println("PostgreSQL JDBC...");
        try {
            Class.forName("org.postgresql.Driver");
        } catch (ClassNotFoundException e) {
            System.out.println("could not find postgreSQL JDBC Driver");
            e.printStackTrace();
            return;
        }
        Connection connection = null;
        try {
            connection = DriverManager.getConnection(
                    "jdbc:postgresql://localhost:5432/postgres",
                    "postgres",
                    "");
        } catch (SQLException e) {
            System.out.println("Connection Failed");
            e.printStackTrace();
            return;
        }

        if (connection != null) {
            System.out.println("connect db successful!");
        } else {
            System.out.println("Failed to make conn!");
        }
        try {
            Statement stmt = connection.createStatement();
            ResultSet rs = stmt.executeQuery("SELECT 1 AS A");
            if (rs != null) {
                rs.next();
                System.out.println(rs.getInt("a"));
            } else {
                System.out.println("null");
            }
            rs.close();
            stmt.close();
            connection.close();
        } catch (Exception exp) {
            exp.printStackTrace();
        }
    }
}