"For循环多次打印数组中的元素"

Question

For this question, I'm trying to make a code which filters out items which have already been purchased from the list. But my for loop is printing all the element from the Item List more than once while also simultaneously ignoring the if condition.

Answer 1

In the loop

    for(int i = 0; i < itemList.length; i++) {
        for(int j = 0; j < itemPurchased.length; j++) {
            if(!itemList[i].equals(itemPurchased[j])) {
                System.out.println(itemList[i]);
            }
        }
    }

Answer 2

The logic of your code is worng. Just replace the last part with:

for(int i = 0; i < itemList.length; i++) {
    boolean alreadyBought = false;
    for(int j = 0; j < itemPurchased.length; j++) {
        if(itemList[i].equals(itemPurchased[j])) {
           alreadyBought = true;
        }
    }
    if(!alreadyBought) {
        System.out.println(itemList[i]);
    }
}

In your code, you check every element in itemList with all the elements in itemPurchased and in case it does not exist then print. This means if your itemPurchased contains n elements, then you will print n time non-bought elements