executable file for java

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Java

netbeans

i am new in java programming

i am trying it through windows platform and ubuntu platform

in c, c++, c#, VB.Net the executable file is .exe

i want to know what is the executable file for java is it .jar ?

and if i want to run my program in my friend computer i only take the .jar file?

how to make it protected?

if the executable file is .jar exactly why i find executable files in ubuntu wuth no extension or .sh and how to make it?

this my code i created the .jar file for it
it works fine but JOptionpane donot work when call it using java -jar database_con.jar in windows and ubuntu

/*
 * To change this template, choose Tools | Templates
 * and open the template in the editor.
 */
package database_con;
import adding.adding;
import com.mysql.jdbc.Statement;
import com.sun.corba.se.spi.orbutil.fsm.Input;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import javax.swing.JOptionPane;
/**
 *
 * @author engamir
 */
public class Database_con {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        // TODO code application logic here
        System.out.println("MySQL Connect Example.");
        Connection conn = null;
        String url = "jdbc:mysql://localhost:3306/";
        String dbName = "test";
        String driver = "com.mysql.jdbc.Driver";
        String userName = "root"; 
        String password = "globalamirtarek";
        com.mysql.jdbc.Statement st=null;
        try
        {
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            conn = DriverManager.getConnection(url+dbName,userName,password);
            System.out.println("Connected to the database");
            st=(Statement) conn.createStatement();
            ResultSet rs;
            //st.executeUpdate("insert into name values(4,'noura')");
            st.executeUpdate("Delete from name where name_id=2");
            rs=st.executeQuery("Select* from name");
            int name_id;
            String name;
            while(rs.next())
            {
                name_id=rs.getInt("name_id");
                name=rs.getString("name");
                System.out.printf("%d    %s\n",name_id,name);
            }
            System.out.println("Disconnected from database");
            
        } 
        catch (ClassNotFoundException | InstantiationException | IllegalAccessException | SQLException e) 
        {
            System.out.println(e.getMessage());
        }
        int z=adding.add(5, 6);
         System.out.print(z);  
         z=JOptionPane.showConfirmDialog(null,"is the number of the result is 11?","The result",1);
         String name=JOptionPane.showInputDialog("what is your name?");
         if(z==0)
         {
             System.out.printf("thanks %s the result is great", name);
         }
         else if(z==1)
         {
             System.out.printf("thanks %s but the result is wrong", name);
         }
         else if(z==2)
         {
             System.out.printf("go to hell %s", name);
         }
    }
}

the lib folder with the .jar file contain the jar file of the driver of mysql com.mysql.jdbc.Driver

and the jar of the class library project adding