Java中的骰子游戏（从带有构造函数的类中调用）

Question

I'm trying to make a dice game with a dice that can give a random number between 1 to 6. I have a class that is called Die which consist of one constructor and two methods. The constructors main purpose is to initiate a random value and the two methods should roll the dice and return the value respectively. My problem is that I don't know how to roll the dice and retrieve the number after I have made an object.

import java.util.Random;

class Die{
    int dots,roll;
    Random number = new Random();

    public Die(){
        int dots = number.nextInt(6)+1 ;
    }

    public void roll(){
        roll = number.nextInt(dots)+1;
    }

    public int getDots(){
        return roll;
    }

}

public class Uppg1 {
    public static void main (String args[]){
        Die die = new Die();
        System.out.println("Du fick "+die.getDots());

    }
}

It appears that my code goes to the constructor and not to methods. I want the value from the constructor and then roll the dice and then get the value from method getDots.

Answer 1

Inside Die constructor you update internal dots variable instead of class member. Use:

public Die(){
    dots = number.nextInt(6)+1 ;
}

Answer 2

  int dots = number.nextInt(6)+1 ;

This is different variable from the variable

class Die{
    int dots,roll;

so make it

dots = number.nextInt(6)+1 ;

so that you will get the right value.

Answer 3

I have modified the code for you just take a look:import java.util.Random;

class Die{
    int dots,roll;
    Random number = new Random();

    public Die(){
         dots = number.nextInt(6)+1 ;
    }

    public void roll(){
        roll = number.nextInt(dots)+1;
    }

    public int getDots(){

        return roll;
    }

}

public class Uppg1 {
    public static void main (String args[]){
        Die die = new Die();
        die.roll();
        System.out.println("Du fick" +die.getDots());

    }
}

remove int from Die constructor as it already defined as global, your prog. doesn't call roll method anywhere hence need to call that.

Answer 4

int dots = number.nextInt(6)+1 does not change the field dots but creates a new variable dots

Additionally you never call roll() so roll=null and getDots() returns null.

You can roll the dice by calling die.roll() in the Uppg1 main method.