How to Instantiate Classes while passing randomized values from 1 to 6 but each randomized value is passed exactly twice

Question

I want to create 12 instantiations of a class and pass a random value as its parameter. The random values should only range from 1 to 6 BUT I need each value from the range to be distributed twice among the 12 instances of the class.

The constructor of the Class is as follows:

Die(int numSide){
    this.numside = numSide;
}

Basically, I want to create 12 instances of dice with 2 of each side, sort of, as a result of a tossing.

Answer 1

Add the numbers 1 to 6, twice to an ArrayList. Now pick a random index from that last and pass that to your Die constructor. Remove that index from the pool so it doesn't get used again.

Something like:

  public static void main( String [] args) {   
    List<Die> dice = new ArrayList<Die>();
    List<Integer> pool = new ArrayList<Integer>();
    for(int i=1; i<=2; i++) {
      for(int num=1; num<=6; num++) {
        pool.add(num);
      }
    }

    while (pool.size() > 0) {
      int index = (int)(Math.random() * pool.size());
      dice.add(new Die(pool.get(index)));
      pool.remove(index);
    }

    for(Die d : dice) {
      System.out.println(d.numside);
    }
  }

My output:

2
3
3
1
4
6
5
6
4
5
2
1

An alternative approach would be to add the Die instances directly to the Dice arraylist from the nested for loops, then simply pull a random instance from that list and remove it. Same concept as the pool, just depends on whether you need to use and/or keep that random order of Die instances for something else.

Answer 2

Your Question is confused. So I will focus on:

pass a random value

…

range from 1 to 6 BUT I need each value from the range to be distributed twice

IntStream

You can use IntStream to generate numbers.

Put together two streams of 1-6 inclusive. Generate an array from their output. Shuffle that array. Loop that array to get each int value.

int[] oneThruSixTwice = 
    IntStream.concat
    (
        IntStream.rangeClosed( 1 , 6 ) ,
        IntStream.rangeClosed( 1 , 6 )
    )
    .toArray() ;
Collections.shuffle( oneThruSixTwice ) ;
for( int x : oneThruSixTwice )
{
    …
}

Answer 3

Building on @Basil Bourque (though note you can't shuffle an array with Collections ) you could do:

    List<Die> dice = IntStream.concat(
            IntStream.rangeClosed(1, 6),
            IntStream.rangeClosed(1, 6))
                .mapToObj(i -> new Die(i))
                .collect(Collectors.toList());
    Collections.shuffle(dice);
    dice.stream()
        .forEach(
            die -> System.out.printf("Die with %d side(s) rolled %d%n", die.getNumSides(), die.roll()));

On the last run, this gave me:

Die with 5 side(s) rolled 4
Die with 4 side(s) rolled 1
Die with 6 side(s) rolled 2
Die with 4 side(s) rolled 3
Die with 1 side(s) rolled 1
Die with 3 side(s) rolled 2
Die with 5 side(s) rolled 5
Die with 1 side(s) rolled 1
Die with 3 side(s) rolled 3
Die with 2 side(s) rolled 2
Die with 2 side(s) rolled 1
Die with 6 side(s) rolled 1