如何在 Java 中生成多个随机变量？

Question

I am making a game where the user gets to pick the number of die for each roll. Right now my code is processing the users input correctly, but it only randomly generates the last number, the other numbers are 0. (For example if the user input 4 the roll would appear: [0,0,0,3] Does anyone know how to get all the numbers to generate random numbers? Here is my main:

public class game
{
    public static void main(String[] args) 
  {
    int play = 1, sum = 0;
    int[] wins = new int[15];
    
    while ((play == 1) && (sum < 15)) 
    {
      sum = 0;;
      
      int roll = 0;
      Config die= new Config();
      //starts configuration
 
     
    die.hand();
    
      System.out.println("\nHere is your roll:\n");
      die.get();
    }
}

Here is my configure class:

import java.util.Scanner;
import java.util.Random;
import java.util.Arrays;

class Config
{
    public static int Dice;
    int i;
    public void hand()
    {
        System.out.println("\nLet's Configure the Game...\n");
    
        String file = "Config.txt";
        Scanner scan = new Scanner(System.in);

        //configures number of dice in hand
        System.out.println("Enter the number of dice you would like in your hand (1-5): ");
        int hand_count = scan.nextInt();
        int[] Dice = new int[hand_count];
        System.out.println("Here is your roll: \n");
        Random random= new Random();
        
       for (i = 0; i<hand_count - 1; i++);
        { 
            Dice[i] = random.nextInt(6) + 1; 
            System.out.println(Arrays.toString(Dice)); 
        }
        

        System.out.println("\nNow lets play the game...\n"); 
    
//s.close();
    }
    public int get()
    {
        return Dice;
    }
}

Answer 1

for (i = 0; i<hand_count - 1; i++);
        { 
            Dice[i] = random.nextInt(6) + 1; 
            System.out.println(Arrays.toString(Dice)); 
        }

You have a semi-colon at the end of the first line of this for loop, resulting in your loop having no contents. Get rid of the semi-colon, and move your opening curly brace onto the same line as the for loop, ie

for (i = 0; i<hand_count - 1; i++) {
  // do cool stuff
}

Answer 2

The answer by sunrise is good. But I suggest using ThreadLocalRandom instead of java.util.Random . Plus, your code has other issues to resolve.

ThreadLocalRandom

Using the ThreadLocalRandom class is thread-safe in case you ever use background threads. And a single random-number generator per thread is established, available automatically for re-use, so less overhead for repeated use.

Like java.util.Random , ThreadLocalRandom offers some nifty methods for generating a series of numbers as a stream for use in modern Java. We can shorten the code to a single-line.

int countDice = 3;

// Bounds of random number are inclusive, exclusive. So (1,7) for six-sided dice.
int[] results = ThreadLocalRandom.current().ints( countDice , 1 , 7 ).toArray(); 

System.out.println( "results = " + Arrays.toString( results ) );

When run:

results = [4, 6, 4]

Other issues

Variable names should start in lowercase. So public static int Dice; should be public static int dice; .

Class names start in uppercase, by convention. So public class game should be public class Game .

Your class design is disorganized. A key goal of object-oriented programming (OOP) is to more clearly model the entities being represented within your app. So I suggest you create a Die class to represent each die. That class should have a roll method that generates a new value.

In another class, instantiate some of these Die objects. Collect those instances in a collection named dice . Then for each round of your game, call roll on each die.

I was tempted to write more code for you, but this is obviously homework I'll go no further.