Java Dice Roller

Question

I've written a basic dice program in Java which takes a number of faces then randomly selects a number within that boundary. Here is the code:

package com.georgegibson.diceroller;
import java.util.Random;
import java.util.Scanner;
public class DiceRoller
{
 public static void main(String []args)
 {
 Random dice = new Random();
 Scanner input = new Scanner(System.in);
 int faces;
 int result;
 System.out.println("Dice Roller\n");
 System.out.println("How many faces does the dice have?");
 faces = input.nextInt();
 result = dice.nextInt(faces) + 1;
 System.out.println("\nThe dice rolled a " + result + ".");
 }
}

Seen as I am pretty new to Java (I come from C/C++ land), I should think this can be improved, but how?

EDIT: I know I should have a different package name, but I am going to get that domain (georgegibson.com).

Answer 1

In your code you have declared a variable dice which is a Random. This is an indication that you have a mismatch between the object and the implementation. The fact that you call it 'dice' implies you want something that is a Dice.... not a Random. A Dice should be able to "encapsulate" itself.

I would suggest a clean Java object oriented design would have a Dice class, something like:

public class Dice {
 private final Random rand;
 private final int faces;
 public Dice(int faces) {
 this.rand = new Random();
 this.faces = faces;
 }
 public int roll() {
 return 1 + rand.nextInt(faces);
 }
}

Now you have a class that represents a dice, and you can roll that dice, and you now have a main method that looks like:

public static void main(String []args)
{
 Scanner input = new Scanner(System.in);
 System.out.println("Dice Roller\n");
 System.out.println("How many faces does the dice have?");
 Dice dice = new Dice(input.nextInt());
 System.out.println("\nThe dice rolled a " + dice.roll() + ".");
}

You can reuse that dice, or create other dice with a different number of faces.

Note, there's always going to be a discussion about the singular is "Die", and the plural is "Dice". One Die, many Dice.... but I say "who cares" call it a Dice.... Creating a class called "Die" is just wrong ;-)

Answer 2

Unlike in C, in Java people usually declare the variables when they actuall need them; for example:

System.out.println("How many...");
int faces = input.nextInt();
int result = dice.nextInt(faces) + 1;

Also, what comes to braces, more idiomatic style is

public class DiceRoller {
 ...
 public static void main(String[] args) {
 ...
 }
}