JDBC Example

import java.sql.*;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import static java.lang.System.out;

public class DBEG {
    public static void main (String[] args) {

        /*
            args[0] => database name
            args[1] => table name
            args[2] => user
            args[3] => pass

            java DBEG.java OCPJP sample root XXXX

            sudo mysql -u root -p
            SET GLOBAL validate_password.policy=LOW; //default is MEDIUM
            SET GLOBAL validate_password.length=4;
            SET GLOBAL validate_password.mixed_case_count=1;
            SET GLOBAL validate_password.number_count=0;
            SET GLOBAL validate_password.special_char_count=1;
            ALTER USER 'root'@'localhost' IDENTIFIED BY 'XXXX';

            For MariaDB on Fedora 29:
            https://www.if-not-true-then-false.com/2013/install-mariadb-on-fedora-centos-rhel/

            USE OCPJP
            ALTER TABLE sample ADD PRIMARY KEY (col1);

        */

        String mySQL = new StringBuilder("jdbc:mysql://localhost:3306/").append(args[0]).toString();
        String postgreSQL = new StringBuilder("jdbc:postgresql://localhost:5432/").append(args[0]).toString();
        BufferedReader inpt = new BufferedReader(new InputStreamReader(System.in));
        ResultSetMetaData rsmd = null;
        DatabaseMetaData dbmd = null;
        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;
        String query = null;

        try {

            con = DriverManager.getConnection(mySQL, args[2], args[3]);
            dbmd = con.getMetaData();
            stmt = con.createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_UPDATABLE);
            stmt.closeOnCompletion();
            var warnings = con.getWarnings();

            do {
                out.print("\nEnter SQL Query:  ");
                query = inpt.readLine();

                if (query.toLowerCase().equals("exit")) {
                    try {
                        inpt.close();
                        stmt.close();
                        // con.close();
                    } catch (Exception e) { e.printStackTrace(); }
                    finally {
                        System.exit(0);
                    };
                }

                else {
                    rs = stmt.executeQuery(query);
                    rsmd = rs.getMetaData();
                    out.println("JDBC Driver Name: [" + dbmd.getDriverName() + "]");
                    out.println("Database Product Name: [" + dbmd.getDatabaseProductName() + "]");
                    out.println("Local Database Name (Relative): [" + dbmd.getURL().substring(dbmd.getURL().lastIndexOf("/") + 1) + "]");
                    out.println("Local Database Name: [" + dbmd.getURL() + "]");
                    out.println("Connection Object Catalog: " + con.getCatalog());
                    out.println("Table Name: [" + rsmd.getTableName(1) + "]");
                    //calculate the amount of rows
                    rs.last(); int rowct = rs.getRow(); rs.beforeFirst();
                    //----------------------
                    out.println("Row Count in ResultSet:  " + rowct);

                    while(rs.next()) {
                        out.println("\t[col1]:\t" + rs.getString("col1"));
                    };

                    while (true) {
                        if (warnings == null) {
                            out.println("No warnings bro.");
                            break;
                        }
                        else
                            out.println(warnings.getNextWarning());
                    }

                    //Insert Row Demo
                    rs.first(); //1
                    rs.next(); //2
                    out.println("Row before insert row:  " + rs.getRow());
                    rs.moveToInsertRow();
                    out.println("What is the index of the insert row?:  " + rs.getRow());
                }
            } while (!query.toLowerCase().equals("exit"));

        }  catch (SQLSyntaxErrorException sre) {
            out.println("Your SQL query is malformed.");
        }
        catch (SQLException | IOException sqie) {
            sqie.printStackTrace();
            while (true) {

                if (sqie instanceof SQLException) {
                    SQLException se = ((SQLException) sqie).getNextException();
                    if (se == null) {
                        out.println("No Exceptions bro.");
                        break;
                    }
                    else
                        out.println(se);
                }
            }
        } finally {
            try {
                if (inpt != null)
                    inpt.close();
                if (rs != null)
                    rs.close();
                if (!stmt.isClosed())
                    stmt.close();   //no longer needed
                if (!stmt.isClosed())
                    con.close();
            } catch (SQLException | IOException e) { e.printStackTrace(); };
        };

    };
};