Fill the array with numbers from 1000 to 10000-1

Question

Good day! I create an array of integer values, the values from 1000 to 9999, inclusive, should be entered into it via for when the program starts. Then I randomly click on a button and select one of the values. I put the size of the array 10,000. As a result, I often get the value 0, although if I output the entire array to the console, then there are no such values. Help me to understand! In the end, at the press of a button, I have to get only one 4-digit number ...

I create an array:

public int passArray[] = new int[10000];

I fill in:

 for (int i = 1000; i < passArray.length; i++){ passArray[i] = i; }

I deduce on clicking of the button:

 int index; index = passArray[(int) (Math.random() * passArray.length)]; System.out.println(Integer.toString(index));

As a result, it gives the number, for example, 3443, then once again, it gives 5534, and once again I press and gives 0, I can give 0 again, in general, I can’t understand where they come from ... Tell me!

Qwertiy ♦ Qwertiy 76k 17 73 199 · Accepted Answer · 2017-10-04T12:46:33

 for (int i = 1000;

And what do you think in the array in the elements from 0 to 999? That's just 0.

 int index; index = passArray[; System.out.println(Integer.toString(index));

 System.out.println(Integer.toString((int)(Math.random() * 9000) + 1000));

Answer 2 · 2017-10-04T12:45:59

The array is initialized with zeros. In an array of 10,000 items, and you reinitialize only 9000.

10% chance of getting zero.

UPDATE:

 public int passArray[] = new int[9000]; for (int i = 0; i < passArray.length; i++){ passArray[i] = i+1000; }

Or as in the answer Qwertiy.

I also thought about it, but how to reduce the size to fill 9000 starting from 1000 I did not understand .... I already broke my whole head) tell me?
@Qwertiy, yes, I tried it just ... I had the idea that up to 1000 zeros, but I didn’t know how to “filter” when choosing a number ... and where I didn’t think of slipping this “+1000” )) thank!

Fill the array with numbers from 1000 to 10000-1

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