随机打印数组元素，直到已打印所有元素

Question

I'm trying to create a method that takes in 3 int arrays and prints out one element from each array until all the elements of all three arrays have been printed at least once. The first array has 10 elements, the second has 7, and the third has 2. The elements are selected and printed at random. Any help would be appreciated. The idea is to see how many iterations it would take to print out all the elements at least once. I don't know the conditions to set for a large scale iteration like this. My code so far (with just one array as a parameter):

import java.util.*;

public class calculateAverage{

  private static int[] x = new int[]{1,2,3,4,5,6,7,8,9,10};
  private static int[] y = new int[]{1,2,3,4,5,6,7};
  private static int[] z = new int[]{1,2};



  public static void main(String[] args){    
    calculate(x);

  }

  public static void calculate(int a[]){
    Random random = new Random();
    for(int i = 0;i < a.length; i++){
      System.out.print(a[random.nextInt(a.length)] + " ");
    }
    System.out.println();
  }

}

code output: 7 2 4 1 8 10 3 10 7 3

Answer 1

You could use a collection like Set to keep track of indexes that were already picked. Each time you generate a random number you would first check if it already exist in the Set. If not, print the value in array and add the index number to the set.

Your loop would end when size of that set equals size of the array.

Answer 2

Solution for one array:

public static int calculate(int a[]){
    Random random = new Random();
    HashSet<Integer> remaining = new HashSet<Integer>();
    for (int i = 0; i < a.length; i++) {
        remaining.add(i);
    }
    int i = 0;
    while (!remaining.isEmpty()) {
        int index = random.nextInt(a.length);
        System.out.print(a[index] + " ");
        remaining.remove(index);
        i++;
    }
    System.out.println();
    System.out.println("Finished after " + i + " iterations.");
    return i;
}

Answer 3

int a[] = {4, 6, 3, 2, 9, 1, 5};        
Set<Integer> set = new TreeSet<Integer>();
int counter = 0;
Random rand = new Random();
while(set.size() != a.length){
    set.add(a[rand.nextInt(a.length)]);
    counter ++;
}
System.out.println("Total Iterations : "+counter);
return counter;