Scanner in method (do loop) not accepting greater/less than sign

Question

I have an assignment where I need to make a Roulette program using a java program (Im using Eclipse). The program has a requirment that states: Given the following method heading , you must write the corresponding definition for a int return method that reads, validates, and returns a number to bet on, which must be between 0 and 36. (The heading is public static int getNumber(Scanner stdIn) ). The problem I'm having is with the while statement, because it doesnt recognize the greater/less than symbol. How do I go about fixing this?

import java.util.Scanner;
public class Program08 
{
    public static void main(String[]args)
    {
    welcome();
    Scanner stdIn = new Scanner(System.in);
    int number;
    number = getNumber(stdIn);

    }
public static void welcome()
{
    System.out.println("Welcome to Roulette!");
    System.out.println("Number bets payout: 35:1");
}
public static int getNumber(Scanner stdIn)
{
    do
    {
        //int play;
        System.out.println("Enter the number to bet on [0-36]: ");
        //play = stdIn.nextInt;
    }
    while (stdIn<0 || stdIn>36);

}
}//end of program

Answer 1

You have compilation errors in your program. Here is the code that compiles correctly,

import java.util.*;

public class Program08{

    public static void main(String[] args){
            welcome();
        Scanner stdIn = new Scanner(System.in);
        int number;
        number = getNumber(stdIn);
    }

    public static void welcome(){
      System.out.println("Welcome to Roulette!");
      System.out.println("Number bets payout: 35:1");
    }

    public static int getNumber(Scanner stdIn){
        int play = 0;
        do{
          System.out.println("Enter the number to bet on [0-36]: ");
          play = stdIn.nextInt();
      } while (play < 0 || play > 36);
        return play;
    }
}

What were the fixes:

1. In getNumber() declare play (the integer variable where you are going to store the choice of the user) outside of the do-while loop. You do that so the while section of the do-while statement can access that variable.
2. Use the Scanner object ( stdIn ) to read a number from the user and store it in play . This does that: play = stdIn.nextInt() (assuming the user will enter a number and not some arbitrary text which would produce an error or more precisely raise an exception ).
3. Compare the value of play in the while section of the do-while statement. What you wrote, stdIn < 0 is fundamentally wrong since you're comparing a Scanner object, which is not a number, to a number. Imagine in place of a Scanner having another object, say a Person . Could you say that George (an instance of Person ) is greater than zero? Obviously you cannot. You could say though that George's age (which is a number) is greater than zero, George.age > 0 .

Answer 2

That's because you have to call the method nextInt() on the scanner to get the actual value.

So outside your loop, declare an int input , set it at the end of the loop and then check that:

int input;

do {
    //... stuff

    input = stdIn.nextInt();
} while(input < 0 || input > 36);