jdbcデータベース接続状態のテスト

jdbcデータベース接続状態のテスト

import java.sql.Connection;
import java.sql.DriverManager;

public class a {
    //  mysql8.0 com.mysql.cj.jdbc.Driver 8.0 com.mysql.jdbc.Driver  jdbc jar 
    private static final String driver = "com.mysql.cj.jdbc.Driver";
    // URL 
    private static final String url="jdbc:mysql://127.0.0.1:3306/demo4?useUnicode=true&characterEncoding=UTF-8&useSSL=false&&serverTimezone=UTC";
    // 
    private static final String username="root";
    // 
    private static final String password="root";

    private static Connection conn=null;

    // 
    static
    {
        try
        {
            Class.forName(driver);
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }
    }

    // 
    public static Connection getConnection() throws Exception
    {
        if(conn==null)
        {
            conn = DriverManager.getConnection(url, username, password);
            return conn;
        }
        return conn;
    }

    public static void main(String[] args) {

        try
        {
            Connection conn =a.getConnection();
            if(conn!=null)
            {
                System.out.println(" ！");
            }
            else
            {
                System.out.println(" ！");
            }
        }
        catch(Exception ex)
        {
            ex.printStackTrace();
        }

    }
}