从ArrayList中删除一个元素

Question

I have an ArrayList which contain 10 elements and a variable int = 12 . Now I want to count how many elements are in array and if are less than 12 to start to count again from 0 and stop to index 2 and remove it, until I will have one element in my array. I tried the following:

int j = 12;
int l = 0;

// Here I check if j is less than array.size
while (j < array.size()) {
    for (int i = 0; i < array.size(); i++) {
        if (j == i + 1) {
            array.remove(i);
        }
    }
}
// Here is for j greater than array.size
while (array.size() != 1) {
    for (int i = 0; i < array.size(); i++) {
        l = j - array.size();
        if (l < array.size()) {
            array.remove(l);
        }
    }
}
System.out.println(array);

UPDATE:

MyArray = {1,2,3,4,5,6,7,8,9,10};
int=12;

MyArray contain just 10 elements, but I want to delete the index with number 12 , as long as index 12 does not exist I should start to count again from zero, and the number 12 is at index 2 , That's why I should delete the index with number 2 . The second iteration MyArray will contain just 9 elements, and again 12-9=3 , I should delete the index with number 3 , until I will have just one element in MyArray

Answer 1

Instead of looping twice through the array to remove the last n elements until the length of the list equals j, you could simply use:

while (j < array.size()) { 
    array.remove(j - 1);
}

If you always want to remove index 2, you could do:

while (array.size() >= 3) { // otherwise you will get a ArrayIndexOutOfBoundsException
     array.remove(2);
}

However, you will have two elements left in your ArrayList instead of 1 (at index 0 and 1). You cannot delete ìndex 2 at that point, because it is not a valid index any longer.

Thus, you could either remove index 0/1 afterwards or what I think you want to achieve:

while (array.size() >= 2) { // otherwise you will get a ArrayIndexOutOfBoundsException
     array.remove(1);
}

Then only one element will remain in your list at index 0.

Edit: for the update of your question it is

int originalSize = array.size();
while (array.size() >= originalSize - j) { // otherwise you will get a ArrayIndexOutOfBoundsException
     array.remove(originalSize - j);
}

However, you will always be left with size - j items in your list. You cannot remove index 3, for example, until you have only one element in your list.

Answer 2

An answer to the updated question:

When you have a list of length 10 and you want to delete the "12th element" you can use the modulo operator:

ArrayList<...> someList = ...;
int toDelete = 12;

int deleteInRange = toDelete % someList.size();
someList.remove(deleteInRange);

The modulo operator will deliver the rest of the integerdivision 12 / 10 ( toDelete % someList.size() )

You can use this code snippet in a loop in order to remove multiple elements.

Answer 3

If you always want to remove index 2, you could do:

l = j - array.size();

Change this line as below:

int sum = 0;
sum = l - array.size();
if (sum > 0) {
    array.remove(sum);
} else {
    sum = array.size() - l;
    array.remove(sum);
}