Generate random numbers 1-12 without null?

Question

Hopefully the title explains what I want. I want a set of numbers 1-12 in a random order but not get a null result.

Here is my code:

Integer[] arr = new Integer[12];

    for(int i = 1; i < arr.length; i++)
    {
        arr[i] = i+1; //With this not being i+1, I get 0-11. Like this, I get null-12 and no 1.

        if (arr[i] ==  null)
        {
            arr[i] = 1;
        }
    }

    Collections.shuffle(Arrays.asList(arr));
    System.out.println(Arrays.asList(arr));

And here is what I get as an output:

[null, 5, 3, 10, 7, 2, 9, 4, 6, 12, 8, 11]

How can I convert the null because my if statement does nothing?

Answer 1

You're not initializing the first element in you array. Start with i = 0 in you loop, like this:

for(int i = 0; i < arr.length; i++)

Answer 2

从0开始而不是1

for(int i = 0; i < arr.length; i++)

Answer 3

Arrays are 0 based , so the first elements should be start from 0 index, not 1

So try to change your code like:

 for(int i = 0; i < arr.length; i++)

for more details read more about arrays .

Answer 4

在0开始for循环

for(int i = 0; i < arr.length; i++)

Answer 5

You are initializing loop variable i to 1 as a result the array arr[0] is never assigned a value which is by default null. Your loop should be for(int i = 0; i < arr.length; i++)