Question

Like my question, i need to generate random numbers that have identical pairs between a range. i have tried to generate random numbers and stored in an array but the numbers are repeating more than twice. i have 16 random numbers to be generated in the range. Any idea how to make it generate only identical pairs random number?

Answer 1

The following will do the job I think :

import java.util.*;

class Randoms {
  public static void main(String[] args) {
    List<Integer> randoms = new ArrayList<Integer>();
    Random randomizer = new Random();
    for(int i = 0; i < 8; ) {
      int r = randomizer.nextInt(8) + 1;
      if(!randoms.contains(r)) {
        randoms.add(r);
        ++i;
      }
    }
    List<Integer> clonedList = new ArrayList<Integer>();
    clonedList.addAll(randoms);
    Collections.shuffle(clonedList);

    int[][] cards = new int[8][];
    for(int i = 0; i < 8; ++i) {
      cards[i] = new int[]{ randoms.get(i), clonedList.get(i) };
    }

    for(int i = 0; i < 8; ++i) {
      System.out.println(cards[i][0] + " " + cards[i][1]);
    }
  }
}

One sample run of the above gives :

1 2
8 6
4 3
3 7
2 8
6 1
5 5
7 4

Hope that helps.