CODEWITHSUNDEEP
javagoto
Austen Clay
Austen Clay

Reputation: 39

Alternative to goto statement in Java

OK, so I'm sure this question has been beaten to death, but I still can't find the answer I need for my project.

I am working on building a casino game suite in java (I'm 110% sure that there are better, and easier languages for this, but I am learning java right now and I'd like to code in java for the practice.) My issue is that I cannot figure out how to structure my code. I am used to using goto statements (I started learning coding in small basic). For example:

import java.util.*;

public class CasinoGames
{
  public static void main(String[] args)
  {
    Scanner keys = new Scanner(System.in);
    sopln("Hello, and welcome to Casino Games!");
    sopln("Would you like to login, register, or play as a guest?");
    char token = keys.nextLine().toLowerCase().charAt(0);
    randomlabelhere:
    if (token == "l")
      User.login();
    else if (token == "r")
      User.register();
    else if (token == "g")
      User.guestLogin();
    else
      sopln("Invalid Choice, please try again!");
      goto somerandomlabel

I know this won't compile, so please don't mention that. I know that I can use a do-while loop for this, but if I wanted the option to do a goto, what alternatives do I have?

Upvotes: 0

Views: 6345

Answers (5)

user3834947
user3834947

Reputation: 

import java.util.Scanner;

public class Casino {

public static void main(String[] args) {
    try (Scanner input = new Scanner(System.in)) {
        sopln("Hello, and welcome to Casino Games!");
        sopln("Would you like to login, register, or play as a guest?");
        while (true) {
            char token = input.next().toLowerCase().charAt(0);
            if (token == 'l') {
                User.login();
                break;
            } else if (token == 'r') {
                User.register();
                break;
            } else if (token == 'g') {
                User.guestLogin();
                break;
            } else {
                sopln("Invalid Choice, please try again!");
            }
        }
    }
}

public static void sopln(String str) {
    System.out.println(str);
}

private static class User {
    static void login() {}

    static void register() {}

    static void guestLogin() {}
}
}

Scanner implements AutoCloseable in Java 7+, so I managed it with the try-with-resources feature.

Note: User should be presented with a menu so they know what l, r, and g stand for. I know it seems obvious, but you'd be surprised :-P

I'd also add some sort of escape case for exiting the program.

I'm trying to think of the last time I used a goto statement, and the only thing that comes to mind is MIPS assembly jump operations.

Upvotes: 0

Cal Stephens
Cal Stephens

Reputation: 793

If you wanted to, you could take everything that would be under the goto and make it it's own method. Say you wanted goto startInteraction, then you could do this:

void startInteraction(){
    //everything below your "randomlabelhere:" would go in this method
}

and then call startInteraction() any time you wanted to trigger that.

A difference is that a goto wouldn't return to where it was called from, while this method would. That feature could be simulated if you used a return; in the line following where you call startInteraction() so that the code doesn't continue following the method call.

Upvotes: 2

MadProgrammer
MadProgrammer

Reputation: 347194

Also, token == "l" is not how String comparison works in Java, you want to something more like "l".equals(token)

Besides, token is a type of char so it should be more like token == '1', but you could get away with using a String and using token.trim().startsWith("1"), but you'd need to test for a null result

Upvotes: 7

jacobm
jacobm

Reputation: 14025

Here's one way you could do it:

import java.util.*;

public class CasinoGames
{
  public static void main(String[] args)
  {
    Scanner keys = new Scanner(System.in);
    sopln("Hello, and welcome to Casino Games!");
    sopln("Would you like to login, register, or play as a guest?");
    while (true) {
      char token = keys.nextLine().toLowerCase().charAt(0);
      if (token == 'l') {
        User.login();
        break;
      }
      else if (token == 'r') {
        User.register();
        break;
      }
      else if (token == 'g') {
        User.guestLogin();
        break;
      }
      else {
        sopln("Invalid Choice, please try again!");
      }
    }
  }
}

Upvotes: 1

Elliott Frisch
Elliott Frisch

Reputation: 201439

The closest thing Java has to a goto are labels for break and continue. Goto has been considered harmful for longer than Java has been a language, and consequently Java doesn't have a goto implementation (and goto is a reserved word so you cannot add one). Finally, since token is a char you should compare with char literals like

while(true) {
  if (token == 'l')
    User.login();
  else if (token == 'r')
    User.register();
  else if (token == 'g')
    User.guestLogin();
  else {
    sopln("Invalid Choice, please try again!");
    continue;
  }
  break;
}

Upvotes: 2

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