Random Number Generator in Java

I'm writing a program that will work like a magic 8 ball. It asks for a question and then prints a random response out of 20 that I've put in it. It doesn't show any errors in the coding, but when I run it the program works perfectly until the point where it would need to print the random response. This is a homework assignment so I'm not looking for someone to correct it, but I'm trying to figure out exactly how to get this to work. Thank you and I appreciate the help.

import java.util.Scanner;


public class MagicBall
{

    public static void main(String[] args)
    {

        Scanner input = new Scanner(System.in);
        System.out.println("Please type in a question: ");
        double question = input.nextDouble();


        int number = (int)(Math.random() * 20);

        if (number == 0)
            System.out.println("As I see it, yes");

        if (number == 1)
            System.out.println("It is certain");

        if (number == 2)
            System.out.println("It is decidedly so");

        if (number == 3)
            System.out.println("Most likely");

        if (number == 4)
           System.out.println("Outlook good");

        if (number == 5)
            System.out.println("Signs point to yes");

        if (number == 6)
            System.out.println("Without a doubt");

        if (number == 7)
            System.out.println("Yes");

        if (number == 8)
            System.out.println("Yes – definitely");

        if (number == 9)
            System.out.println("You may rely on it");

        if (number == 10)
            System.out.println("Reply hazy, try again");

        if(number == 11)
            System.out.println("Ask again later");

        if (number == 12)
            System.out.println("Better not tell you now");

        if (number == 13)
            System.out.println("Cannot predict now");

        if (number == 14)
            System.out.println("Concentrate and ask again");

        if (number == 15)
            System.out.println开发者_开发问答("Don't count on it");

        if (number == 16)
            System.out.println("My reply is no");

        if (number == 17)
            System.out.println("My sources say no");

        if (number == 18)
            System.out.println("Outlook not so good");

        if (number == 19)
            System.out.println("Very doubtful");
    }
}

double question = input.nextDouble();

What makes you think the question would be a floating point number?

Apache commons is very helpfull:

RandomUtils.nextInt(maxVal);

Your code works for me, but it forces you to input a double (e.g. 123.456). You should change:

double question = input.nextDouble();

to:

String question = input.nextLine();

Also, you may want to use a switch statement instead of all those ifs.

Instead of int number = (int)(Math.random() * 20);

Replace with int number = new Random().nextInt(20);

See http://download.oracle.com/javase/1.4.2/docs/api/java/util/Random.html#nextInt(int)