如何在阵列中排列从500到1的数组？ （JAVA）

Question

I'm trying to arrange and printout an array starting at 500 and stopping at 1, I have tried this with the following code, but this will printout starting from 1 and going up to 500:

int [] aftel = new int [501];
for (int teller3 = 500; teller3 > 0; teller3--){
       aftel[teller3] = teller3;
    }
System.out.println(Arrays.toString(aftel));

However using the following code, the array will printout the correct way, but I'm trying to arrange the array fully before printing out values:

int [] aftel = new int [501];
for (int teller2 = 1; teller2 <= 500; teller2++){
        optel500[teller2] = teller2;
        System.out.print(optel500[teller2]+" ");
    }

Answer 1

In your first loop, you're using teller3 as both an index and a value. That means that index 500 will have the value 500, which is the opposite of what you want.

You're also making a bit of confusion with the array size.

The correct way to do this would be to either do the loop straight and subtract the value from 500

int [] aftel = new int [500];
for (int teller3 = 0; teller3 < 500; teller3++){
    aftel500[teller3] = (500 - teller3) + 1;
}

Or do the same to the array index

int [] aftel = new int [500];
for (int teller3 = 500; teller3 > 0; teller3--){
   aftel[500 - teller3] = teller3;
}

Answer 2

Try:

int[] array = IntStream
        .range(0, 500) // get a stream of [0, 499]
        .map(i -> 500 - i) // map it to [500, 1]
        .toArray(); 

Answer 3

The problem here is that you are filling the array backwards. Starting from the most significant index down to index 1. In order to achieve the result you should fill from index 1 to the most significant one.

Introducing another variable like index = 1 and using it in such manner will fix the issue:

int [] aftel = new int [501];
int index = 1;

for (int teller3 = 500; teller3 > 0; teller3--){
    aftel[index] = teller3;
    index++;
}

and alternatively the one liner for loop:

int [] aftel = new int [501];

for (int teller3 = 500, index = 1; teller3 > 0; teller3--, index++){
    aftel[index] = teller3;
}

System.out.println(Arrays.toString(aftel));

Answer 4

The problem is that you set 500 on position 500, but you must set 500 on position 0. This should work:

int [] aftel = new int [501];
for (int teller3 = 500; teller3 > 0; teller3--){
       aftel[500 - teller3] = teller3;
    }
System.out.println(Arrays.toString(aftel));

Answer 5

try like this.

int noOfElements = 500;
int[] array = new int[noOfElements];

for (int i = 0; i < noOfElements; i++){
    array[i] = noOfElements - i;
}

for(int a : array){
    System.out.println(a);
}