1. Download JDBC driver

2. Add driver as Library to project.

3. Add query to connect to database:

import java.sql.*;
 
private void btnTestDbConnectionActionPerformed(java.awt.event.ActionEvent evt) {                                                    
    // TODO add your handling code here:
 
    String database = "acme_crm";
    String table    = "customer";
    String url      = "jdbc:mysql://localhost:3306/acme_crm";
    String username = "root";
    String password = "";
 
    System.out.println("Connecting to database " + database + "...");
 
    // Connect to DB
    try (Connection connection = (Connection) DriverManager.getConnection(url, username, password)) {
        System.out.println("Database connected!");
 
        String sql = "SELECT * FROM `" + table + "`";
        try {
            //PreparedStatement stmt = connection.prepareStatement(sql);
            Statement stmt = connection.createStatement();
            //stmt.execute(sql);
            ResultSet rs = stmt.executeQuery(sql);
 
            // Spit out data
            while (rs.next()) {
                int    id = rs.getInt("id");
                String account_number = rs.getString("account_number");
                String  company_name = rs.getString("company_name");
                System.out.println("[" + id + "] " + account_number + ": " + company_name);
            }
 
            stmt.close();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            connection.close();
        }
    } catch (SQLException e) {
        throw new IllegalStateException("Cannot connect to database " + database, e);
    }
 
}

File com.acme.appname.DbUtils.java:

/*
 * To change this license header, choose License Headers in Project Properties.
 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package com.acme.myapp;
 
import com.mysql.jdbc.Connection;
import java.nio.file.Paths;
import java.sql.*;
import java.time.LocalDateTime;
import java.util.*;
import javax.swing.table.DefaultTableModel;
import com.acme.*;
 
public class DbUtils 
{
    static String dbName   = "acme_crm";
    static String table    = "customer";
    static String dbUrl    = "jdbc:mysql://localhost:3306/acme_crm";
    static String dbUsername = "root";
    static String dbPassword = "";
 
 
    public static DefaultTableModel GetDataModelFromQuery(String sql)
    {
        ResultSet rs = null;
        DefaultTableModel dataModel = null;
 
        System.out.println("Connecting to database " + dbName + "...");
 
        // Connect to DB
        try (com.mysql.jdbc.Connection connection = (com.mysql.jdbc.Connection) DriverManager.getConnection(
            dbUrl, dbUsername, dbPassword
        )) {
            System.out.println("Database connected!");
 
            try {
                //PreparedStatement stmt = connection.prepareStatement(sql);
                Statement stmt = connection.createStatement();
                //stmt.execute(sql);
                rs = stmt.executeQuery(sql); // get data
 
                dataModel = DbUtils.GetDataModel(rs);
 
                stmt.close();
            } catch (SQLException exc) {
                exc.printStackTrace();
            } finally {
                connection.close();
            }
        } catch (SQLException exc) {
            throw new IllegalStateException("Cannot connect to database " + dbName, exc);
        }
        return dataModel;
    }
 
    public static DefaultTableModel GetDataModel(ResultSet rs)
    {
        DefaultTableModel dataModel = null;
 
        try {
            ResultSetMetaData rsMetaData = rs.getMetaData();   // get metadata
 
            // Get datamodel
            Vector colNames = DbUtils.GetColNamesAsVector(rs);
            dataModel = new DefaultTableModel(colNames, 0);
 
            // Print out data
            while (rs.next()) {
                // Get column data
                int colCount = rsMetaData.getColumnCount();
                Vector colData = new Vector();
                for (int i=0; i<colCount; i++) {
                    colData.add(rs.getObject(i+1));
                }
                dataModel.addRow(colData);
            }
        } catch (SQLException exc) {
            exc.printStackTrace();
        }
 
        return dataModel;
    }
 
    public static int GetRowCount(String tableName)
    {
        int count = 0;
        try (com.mysql.jdbc.Connection connection = (com.mysql.jdbc.Connection) DriverManager.getConnection(
            dbUrl, dbUsername, dbPassword
        )) {
            System.out.println("Database connected!");
 
            try {
                Statement stmt = connection.createStatement();
                ResultSet rs = stmt.executeQuery("SELECT COUNT(*) AS rowcount FROM " + tableName);
                rs.next();
                count = rs.getInt("rowcount");
                rs.close();
                System.out.println(tableName + " has " + count + " row(s).");
        } catch (SQLException exc) {
                exc.printStackTrace();
            } finally {
                connection.close();
            }
        } catch (SQLException exc) {
            throw new IllegalStateException("Cannot connect to database " + dbName, exc);
        }
        return count;
    }
 
    public static int GetColCount(ResultSet rs)
    {
        int colCount = 0;
 
        try {
            ResultSetMetaData rsMetaData = rs.getMetaData();
            colCount = rsMetaData.getColumnCount();
        } catch (SQLException exc) {
            exc.printStackTrace();
        }
 
        return colCount;
    }
 
    public static Object[] GetColNamesAsObject(ResultSet rs)
    {
        Object[] objColNames = null;
        try {
            ResultSetMetaData rsMetaData = rs.getMetaData();
 
            // Get column names
            int colCount = rsMetaData.getColumnCount();
            objColNames = new Object[colCount];
            for (int i=0; i<colCount; i++) {
                objColNames[i] = rsMetaData.getColumnLabel((i+1));
            }
        } catch (SQLException exc) {
            exc.printStackTrace();
        }
 
        return objColNames;
    }
 
    public static Vector GetColNamesAsVector(ResultSet rs)
    {
        Vector colNames = new Vector();
 
        try {
            ResultSetMetaData rsMetaData = rs.getMetaData();
 
            // Get column names
            int colCount = rsMetaData.getColumnCount();
 
            for (int i=0; i<colCount; i++) {
                colNames.add(rsMetaData.getColumnLabel(i+1));
            }
        } catch (SQLException exc) {
            exc.printStackTrace();
        }
 
        return colNames;
    }
}

Call the query from main to populate a JTable component called tblCustomers:

//...
private void btnTestDbConnectionActionPerformed(java.awt.event.ActionEvent evt) {                                                    
    String sql = "SELECT id, account_number, company_name FROM `" + table + "`";
    tblCustomers.setModel(DbUtils.GetDataModelFromQuery(sql));
}

• YouTube: Connecting to MySQL Database
• StackOverflow: Connect Java to MySQL Database