achieving the same result but using a different kind of loop

Question

so this method performs daily checks that adds one day to the displayedDays in order to determine the freshness of an item, so the method adds a day then check if it's rotten by calling the method isRotten() and if it's rotten it removes it the array

    for (int i = 0; i < numItems; i++) {
        items[i].displayedDays++;
    }

    for (int i = 0; i < numItems;) {

        if (items[i].isRotten()) {
            if (removeItem(i)) {
                if (i > 0) {
                    i--;
                }
                continue;
            }
        }

        i++;
    }

this is also another method that uses the same loop and if's so this method is supposed to remove the sweets from the array ( the array has two types of items bread and sweets)

    double totalSweetsPrice = 0;

    int count = numItems;

    for (int i = 0; i < count;) {
        Item item = items[i];

        if (item instanceof Sweet) {
            totalSweetsPrice += item.getPrice();
            if (removeItem(i)) {
                if (i > 0) {
                    i--;
                }
                continue;
            }
        }
        i++;
    }

and I don't understand the middle part and was hoping that there is a different loop or something whilst getting the same result

this was how a wrote the daily check method

    for (int i = 0; i < numItems; i++) {
    items[i].displayDays++ ;
    if(items[i].isRotten())
    removeItem(i); }

and the output was wrong

Answer 1

As FooBar said, you can’t both iterate an ArrayList and remove items from that same ArrayList. So you need to separate the conditions. For example:

for (int i = 0; i < items.size(); i++) {
    items.get(i).displayedDays++;
}

int i = 0:
while (i < items.size()) {
    if(items.get(i).isRotten()) {
        items.remove(i);
        // don’t increment our counter here because now 
        // we’ve changed what object exists in the ArrayList 
        // at this index position
    } else {
        // only increment our counter if the item in that index
        // is good, so we can now move on to check the next item
        i++;
    }
}