PLEASE HELP IT has an error and I DONT KNOW WHERE

import java.util.*;
import java.io.*;

public class Order {
   private String OrderNumber;
   private double ItemPrice;
   private int Quantity;
   static int selection;
   double Total;
   
    public void setOrderNumber(String OrderNo)
    {
         OrderNumber = OrderNo;
    }      

    public void setItemPrice(double Price)
    {
         ItemPrice = Price;
    }      

    public void setQuantity(int Qnty)
    {
         Quantity = Qnty;
    }        

    public String getOrderNumber()
    {
         return OrderNumber;
    }
    
    public double getItemPrice()
    {
         return ItemPrice;
    }

    public int getQuantity()
    {
         return Quantity;
    }    

    Order(String OrderNo, double Price, int Qnty)
    {
      OrderNumber = OrderNo;
      ItemPrice = Price; 
      Quantity = Qnty; 
    }
    
    public double ComputeTotal(double ItemPrice, int Quantity)
    {
      Total = (ItemPrice * Quantity)+ 0.12;
      return Total;
    }
    
    public void displayOrderDetails()
    {
      System.out.println("Order Number:"+ OrderNumber);
      System.out.println("ItemPrice:"+ ItemPrice);
      System.out.println("Quantity"+ Quantity);
    }
}

it gives me this error please help {Error: Main method not found in class Order, please define the main method as:    public static void main(String[] args) or a JavaFX application class must extend javafx.application.Application}