如何将成员添加到团队

Question

I want the program to go back to the Menu when the switch cases has been completed or is over but i don't know how to do it. here's my code. example, when the user has chosen his/her choice and he/she has performed it the program closes automatically, but i don't want that i want it to continue until the user wishes to exit the program. please help i don't know what to do

    public class Jproj
    {
        public static void main(String[] args)
        {
            boolean back = false;
            String teamone = null;
            String teamtwo = null;
            LinkedList x = new LinkedList();
            String name;
            int team;
            char choice = 'w';


            int num=0;
            System.out.println("Menu");
            System.out.println("a.) Add a member");
            System.out.println("b.) Define the friends of each member");
            System.out.println("c.) Create two teams");
            System.out.println("d.) Save Data");
            System.out.println("e.) Extract data from file");
            Sysmte.out.println("f.) Exit");
            Scanner ans = new Scanner(System.in);
            System.out.print("Choice:");

             choice = ans.next().charAt(0);

             switch(choice)
             {
        case 'a':

            Scanner a = new Scanner(System.in);
            System.out.println("ADDING MEMBERS");
            System.out.print("Name of the member:");
            name = a.nextLine();
            System.out.println(""+name);

                x.insert(name);
                x.displayone();
                System.out.print("Successfull!");   

            break;
        case 'b':
            System.out.println("DEFINING FRIENDS OF MEMBERS");
            break;
        case 'c':
            System.out.print("Creating TEAMS");
            Scanner scanner = new Scanner(System.in);
            if(teamone!=null&&teamtwo!=null)
            {
                System.out.print("Teams has already been created!\n do you want to replace team names?");
                System.out.print("1-Yes\n2-No");

                int sagot = scanner.nextInt();
                if(sagot != 1)
                {
                    return;
                }
                else
                    System.out.println("CREATING TEAMS");
                    Scanner c = new Scanner(System.in);
                    System.out.print("Enter new Name of Team 1:");
                    teamone = c.nextLine();
                    System.out.print("Enter new Name of Team 2:");
                    teamtwo = c.nextLine();
                    x.teamname(teamone,teamtwo);
            }
            else
                    System.out.println("CREATING TEAMS");
                    Scanner c = new Scanner(System.in);
                    System.out.print("Name of Team 1:");
                    teamone = c.nextLine();
                    System.out.print("Name of Team 2:");
                    teamtwo = c.nextLine();
                    x.teamname(teamone,teamtwo);
                    System.out.print("Teams has been successfully created!");
                    System.out.print("Current members:");
                    x.displaytwo();
            break;
        case 'd':
            System.out.println("SAVING DATA");
            break;
        case 'e':
            break;
        case 'f':
            return;
            enter code herebreak;

     }


  }
}

Answer 1

do {
    System.out.println("Menu");
    System.out.println("a.) Add a member");
    System.out.println("b.) Define the friends of each member");
    System.out.println("c.) Create two teams");
    System.out.println("d.) Save Data");
    System.out.println("e.) Extract data from file");
    Sysmte.out.println("f.) Exit");
    choice = ans.next().charAt(0);

    switch(choice){
        case 'a':

        System.out.println("ADDING MEMBERS");
        System.out.print("Name of the member:");
        name = ans.nextLine();
        System.out.println(""+name);

            x.insert(name);
            x.displayone();
            System.out.print("Successfull!");   

        break;
    case 'b':
        System.out.println("DEFINING FRIENDS OF MEMBERS");
        break;
    case 'c':
        System.out.print("Creating TEAMS");
        if(teamone!=null&&teamtwo!=null)
        {
            System.out.print("Teams has already been created!\n do you want to replace team names?");
            System.out.print("1-Yes\n2-No");

            int sagot = ans.nextInt();
            if(sagot != 1)
            {
                return;
            }
            else
                System.out.println("CREATING TEAMS");
                System.out.print("Enter new Name of Team 1:");
                teamone = ans.nextLine();
                System.out.print("Enter new Name of Team 2:");
                teamtwo = ans.nextLine();
                x.teamname(teamone,teamtwo);
        }
        else
                System.out.println("CREATING TEAMS");
                System.out.print("Name of Team 1:");
                teamone = ans.nextLine();
                System.out.print("Name of Team 2:");
                teamtwo = ans.nextLine();
                x.teamname(teamone,teamtwo);
                System.out.print("Teams has been successfully created!");
                System.out.print("Current members:");
                x.displaytwo();
        break;
    case 'd':
        System.out.println("SAVING DATA");
        break;
    case 'e':
        break;
    default:
            System.out.println("Invalid Option");
        break;
    } while (choice != 'f');

use a loop, in this case I'm using a do while loop to reloop the menu. Bring down your println options so it prints the menu for the user to see again. Your choice should be inside the loop too.

Also you are creating a lot of same Scanner object, you just need one and you can re-use it since all of them are using System.in, you are just wasting your memory space by creating same objects for the same use. Look in my case with your codes, I'm using just using the "ans" variable which already stores the Scanner(System.in) and re-use them for any of the user "System Input" (System.in) instead of re-declaring a new one.

Answer 2

try like this!

public class Jproj
{
    public static void main(String[] args)
    {
        boolean back = false;
        String teamone = null;
        String teamtwo = null;
        LinkedList x = new LinkedList();
        String name;
        int team;
        char choice = 'w';

    int num=0;
    while(true){
    System.out.println("Menu");
    System.out.println("a.) Add a member");
    System.out.println("b.) Define the friends of each member");
    System.out.println("c.) Create two teams");
    System.out.println("d.) Save Data");
    System.out.println("e.) Extract data from file");
    Sysmte.out.println("f.) Exit");
    Scanner ans = new Scanner(System.in);
    System.out.print("Choice:");

     choice = ans.next().charAt(0);

     switch(choice)
     {
case 'a':

    Scanner a = new Scanner(System.in);
    System.out.println("ADDING MEMBERS");
    System.out.print("Name of the member:");
    name = a.nextLine();
    System.out.println(""+name);

        x.insert(name);
        x.displayone();
        System.out.print("Successfull!");   

    break;
case 'b':
    System.out.println("DEFINING FRIENDS OF MEMBERS");
    break;
case 'c':
    System.out.print("Creating TEAMS");
    Scanner scanner = new Scanner(System.in);
    if(teamone!=null&&teamtwo!=null)
    {
        System.out.print("Teams has already been created!\n do you want to replace team names?");
        System.out.print("1-Yes\n2-No");

        int sagot = scanner.nextInt();
        if(sagot != 1)
        {
            return;
        }
        else
            System.out.println("CREATING TEAMS");
            Scanner c = new Scanner(System.in);
            System.out.print("Enter new Name of Team 1:");
            teamone = c.nextLine();
            System.out.print("Enter new Name of Team 2:");
            teamtwo = c.nextLine();
            x.teamname(teamone,teamtwo);
    }
    else
            System.out.println("CREATING TEAMS");
            Scanner c = new Scanner(System.in);
            System.out.print("Name of Team 1:");
            teamone = c.nextLine();
            System.out.print("Name of Team 2:");
            teamtwo = c.nextLine();
            x.teamname(teamone,teamtwo);
            System.out.print("Teams has been successfully created!");
            System.out.print("Current members:");
            x.displaytwo();
    break;
case 'd':
    System.out.println("SAVING DATA");
    break;
case 'e':
    break;
case 'f':
    System.exit(0);
 }

}}}