How to fill an array using the for loop in java?

It would be something like this, where you first size the array numbersbased on the variable numand add the values ​​to the array numbers, then print the values ​​stored in the array:

    int num = 7;
    int[] numbers = new int[num];
    
    for(int i = 0; i < numbers.length; i++) { 
        numbers[i] = i+1;              
    }

    
    for (int x : numbers){
        System.out.print(x + " ");
    }

what happens is that python works with lists so it is not necessary to enter the size, in java it should be like this

int num = 7;
      int x = 0;
      List<Integer> numbers = new ArrayList<Integer>();

      for(int i=1;i < num+1;i++){
          
          numbers.add(i);
          
      }
       for(int i= 0;i<numbers.size();i++){
           System.out.print(numbers.get(i) + " ");
       }

or another solution could be this, if instead of lists you want to do it with arrays:

 int num = 7;
  int x = 0;
  int numbers[] = new int[num];
  for(int i=1;i < num+1;i++){
      
      numbers[x]= i;
      x++;
  }
   for(int i:numbers){
       System.out.print(i + " ");
   }

You can use two for loops as usual in java:

int num = 7;
int array[] = new int[num]; // se inicializa el array con un tamaño.
// se llena el array con un ciclo for.
for (int i = 0; i < num; i ++) {
  array[i] = i;
}

// se imprime el array con un for
for (int i = 0; i < num; i++) {
  System.out.print(array[i] + " ");
}

If you want to do it in another way using Java 8, you can do it in the following way:

// genera un rango de números
    IntStream stream = IntStream.range(1, num); 
// el método range devuelve un objeto de tipo IntStream, por lo que se debe convertir a Array.
    int[] arr = stream.toArray();
// Se imprime sin hacer uso de for mediante la claseArray y su método toString()
    System.out.println(Arrays.toString(arr));

Here is the example so you can run it online.

There are five things, first you need to close a brace ( }), the second is that the reason why this does not work for you:

int num = 5;
    for(int i = 0; i < num; i++) {
        int array[] = {};
        array.append[i]
    }

It is because you are creating the array within the loop and then it is being destroyed , what happens is your array, when created within the for , will only exist within the for.

The third thing is that, keep in mind that pythonthings work very differently, pyhon when you declare a arrayyou do not need to specify the number of spaces you want it to have .

In javathis it is different, because for that type of arrays you must always define a size , therefore they are called fixed memory arrays , and there is nothing you can do so that you can use them as dynamic memory arrays , that is to say that once you set the values ​​that the array is going to have or the amount of spaces it is going to have array , the only way to change the amount of memory or spaces that the array is going to use is by redeclaring it, which directly empties the memory.

So that you understand me better, the fourth error is that you have this:

int array[] = {};

That is wrong, it must be corrected, since they [] do not go after the name of the variable, they go after the type in this way:

int[] array = {};

Now that that little detail is corrected, keep in mind that when you use curly braces ( {}) after the equal, it's because what you're trying to do is assign values ​​directly to the array, so you could do something like this and it would work:

int[] array = {0, 1, 4, 10};

However when you leave the keys empty:

int[] array = {};

It is the equivalent of saying that you are not going to save anything in your array and you cannot save anything , that is, you are defining your array with a memory space of 0elements:

int[] array = new int[0];

That would be the other way of declaring an array with xspaces in memory, but without directly assigning values, that is, it would be like having empty spaces in memory assigned that you can later fill.

The fifth problem is that in this line you forgot a ;at the end, I have added it for you:

array.append[i];

That said, let's make the correction to your code:

//El espacio en memoria que tendra el array
int num = 5;
//Creamos un array de 5 espacios basados en num
int array[] = new int[num];

    for(int i = 0; i < array.length; i++) {
        //accedemos al arreglo en la pocision i (array[i]) y le asignamos i.
        array[i] = i;
    }

If you want to see the result you can then print later array:

System.out.println(array);