Java Array of unique randomly generated integers

Question

public static int[] uniqueRandomElements (int size) {

    int[] a = new int[size];

    for (int i = 0; i < size; i++) {
        a[i] = (int)(Math.random()*10);
         


        

Answer 1

 import java.util.Scanner;
 class Unique
{
public static void main(String[]args)
{
    int i,j;
    Scanner in=new Scanner(System.in);
    int[] a=new int[10];
    System.out.println("Here's a unique no.!!!!!!");
    for(i=0;i<10;i++)
    {
        a[i]=(int)(Math.random()*10);
        for(j=0;j<i;j++)
        {
            if(a[i]==a[j])
            {
                i--;

            }
        }   
    }
    for(i=0;i<10;i++)
    {
        System.out.print(a[i]);
    }
}
}

Answer 2

    int[] a = new int [size];

    for (int i = 0; i < size; i++) 
    {
        a[i] = (int)(Math.random()*16); //numbers from 0-15
        for (int j = 0; j < i; j++) 
        {
            //Instead of the if, while verifies that all the elements are different with the help of j=0
            while (a[i] == a[j])
            {
                a[i] = (int)(Math.random()*16); //numbers from 0-15
                j=0;
            }
        }
    }

    for (int i = 0; i < a.length; i++)
    {
        System.out.println(i + ".   " + a[i]);
    }

Answer 3

int[] a = new int[20];

for (int i = 0; i < size; i++) {
    a[i] = (int) (Math.random() * 20);

    for (int j = 0; j < i; j++) {
        if (a[i] == a[j]) {
            a[i] = (int) (Math.random() * 20); //What's this! Another random number!
            i--;
            break;
        }
    }
}