What would you use , golobal or local variabel ???

Question

hello
I must use an object that is going to use a sql connection to perform insert to database .
this object is going to be used 4 times in my class
is it better to use it a global variable ,or to create 4 times this object
here is an example of the use of the local var
class UseVar
     private Connection connection;
     public UseVar(Connection connection)
       this.connection = connection;
    public void method1()
      //some declarations here
      DataBase db = new DataBase(connection);
     db.insertUser("x");
    public void method2()
      //some declarations here
      DataBase db = new DataBase(connection);
     db.deletUser("y");
class DataBase
    public DataBase(Connection connection)
      sqlInsert=connection.prepareStatement("insert into user values( ?)");
      sqlDelete=connection.prepareStatement("delete from user where name = ? ");
    public void inserUser(String name)
      //body of this metod
   public void deleteUser(String name)
      //body of this metod
}the use of the global var would be by declaring the db object in class UseVar as global and then use it in the rest of the methods. my aim is to find the best way to save memory
thank you

Answer 1

It's usually called attribute and not global
variable. Is the connection pooled?
Kajjust to be clear :
Im not talking about the object connection ,Im asking about the object db
DataBase db = new DataBase(connection);any way
my connection is created one time then I pass it from a class to another
so I open the connection one time only
here the class that is called only one time during the program
Class MyConnection
     public MyConnection()
     public  Connection getConnection()
          try
               try
                    Class.forName("org.postgresql.Driver");
               catch (ClassNotFoundException ex)
                    //no dirver found in this pc
                    logger.log(Level.SEVERE, "driver was not found", ex);
                    ex.printStackTrace();
                    System.exit(1);
               connection = DriverManager.getConnection("jdbc:postgresql://" + data_base_server_ip + "/" + data_base_name,
                      data_base_user, data_base_password);
               connection.setAutoCommit(false);
          catch (SQLException se)
               logger.log(Level.SEVERE, "could not connect", se);
               se.printStackTrace();
               System.exit(1);
}Message was edited by:
linuxchild