Best way to create a list of unique random numbers in Java

*Input:
a range in [A, B]
* Output:
a list of unique random numbers from A to B
* For example:
generateRandomNumbers(5, 15)

then output is: 11 13 5 14 12 9 6 8 7 15 10

[rtamilselvim.e.]

after a long search i find an
thanks a
keep rocking like this

[bensmidahoussemeddine]

Hello, in this case the problem that the first case of array "result" result[0] can't contain the last value of a[x-1]
perhaps, we need a random array ?

[shorem]

If I want to get 5 unique random numbers between 20 and 30, it gives unique random numbers from 20 to 24. I should get 27 or 28 etc but this program doesn't give that. There is a bug in it.

[markogilo]

the bug fix for numbers out of range:
for(int i = 1; i <= n; i++)
{
a[i - 1] = i;
}

// an array to store the result
int[] result = new int[n];

SecureRandom rd = new SecureRandom();
int x = n;
for(int i = 1; i <= n; i++)

{
// k is a random index in [0, x]
int k = rd.nextInt(x);

result[i - 1] = a[k];

a[k] = a[x - 1];

x--;
}

[jintsuubest]

i dont get how
a[k] = a[x-1];
x--; will make no duplicate.

Say generateRandomNumbers(0, 5)

int k = 3;
a[3] = a[6-1]; //a[3] = 5
x--; //x = 5
// now it loop
int k = 3; //what prevent this from happening?

I see it work, but I don, t understand, please explain.

[shorem]

You gave the lower limit 4 and upper limit 15, why it gives random numbers less than 4. It should give random numbers equal to or greater than 4 and less than or equal to 15. But it gives numbers less than the lower limit which is 4.

[gurugovindgarg]

same code is generating duplicate values also

[glennviola]

how can i make this start from 1 not from zero?