java sql connection

1import java.sql.*;  
2class MySqlConn{  
3    public static void main(String args[]){  
4        try{  
5            Class.forName("com.mysql.cj.jdbc.Driver");  
6            Connection conn = DriverManager.getConnection("jdbc:mysql://
7            localhost:3306/databasename","username","password");  
8            Statement stmt = conn.createStatement();  
9            ResultSet rs = stmt.executeQuery("select * from emp");    
10            con.close();  
11        }catch(Exception ex){
12            System.out.println(ex);
13        }  
14    }
15}  

1import java.sql.*;
2
3class MySQLConnection{
4
5public static final String DBNAME = "name_of_the_database";  // Like "testDB"
6
7/** JDBC driver name and database URL */
8public static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
9
10/** Gives access to all Databases */
11static final String ALL_DBS_URL = "jdbc:mysql://localhost/?allowPublicKeyRetrieval=true&autoReconnect=true&useSSL=false";
12
13/** Gives access to a given DB */
14static final String GIVEN_DB_URL = "jdbc:mysql://localhost/"+DBNAME+"?allowPublicKeyRetrieval=true&autoReconnect=true&useSSL=false";
15
16// Below are the USERNAME and PASSWORD used in mysql
17public static final String USER = "myUserName";
18public static final String PASS = "myGoodPassWord";
19
20/** A variable for connecting to MySQL Server */
21public static Connection conn = null;
22
23/** A variable for Preparing Statements */
24public static PreparedStatement ps = null;
25
26public static void main(String[] args) 
27			throws ClassNotFoundException, SQLException {
28		// Register JDBC driver
29		Class.forName(JDBC_DRIVER);
30		
31		// Open a connection with MySQL server
32		System.out.println("Connecting to all Databases path...");
33		conn = DriverManager.getConnection(ALL_DBS_URL, USER, PASS);
34		System.out.println("Connected to all Databases!");
35		
36		// Test if there is the db in MySQL Server
37		// if not then create one
38		System.out.println("Testing if "+DBNAME+" exists...");
39		ps = conn.prepareStatement("CREATE DATABASE IF NOT EXISTS "+DBNAME+";");
40		ps.executeUpdate();
41		// Now db exists for sure!
42		
43		// Open a connection with given DB
44		System.out.println("Connecting to "+DBNAME+" path...");
45		conn = DriverManager.getConnection(GIVEN_DB_URL, USER, PASS);
46		System.out.println("Connected to "+DBNAME+"!");
47  		
48  		// then you can do all sort of queries that you want to do
49}
50}

1public void commit() throws SQLException {
2  getConn().commit();
3  if (logger.isTraceEnabled()) {
4    logger.trace("Batch executor commit " + idx.get() + " rows");
5  }
6  idx.set(0);
7}
8