import javax.swing.*;

public class Shop{

public static void main(String [] args){

Shop shop = new Shop();

String mainMenu= "(MAIN SCREEN )";
mainMenu+= "\n1) Computer Menu";
mainMenu+= "\n2) Storage Menu";
mainMenu+= "\n3) Transaction Menu";
mainMenu+= "\n4) Exit";
mainMenu+= "\nPlease select your choice:";

int choice = Integer.parseInt(JOptionPane.showInputDialog(mainMenu));
while (choice!=4);
switch(choice){
case 1:
shop.computerMenu();
break;
case 2:
break;
case 3:
break;
case 4:
break;
}

}
public void computerMenu(){
String computerMenu= "Computer Menu";
computerMenu+= "\n1) Buy Computer";
computerMenu+= "\n2) Sell Computer";
computerMenu+= "\n3) View Computer";
computerMenu+= "\n4) Back To Main Menu";
computerMenu+= "\nPlease select your choice:";

int choice1 = Integer.parseInt(JOptionPane.showInputDialog(computerMenu));

}

}