我想在我的 arrayList“顏色”中存儲沒有配對的數字，但我的 arrayList 收到此運行時錯誤。main 獲取 n（數組大?。┑妮斎牒?arItems 的輸入，然后將 arItems 中的元素轉換為整數，將它們放入 int 數組 ar 中，然后當它調用 sockMerchant 時，它傳遞 int n 和 int 數組 arstatic int sockMerchant(int n, int[] ar) {    ArrayList<Integer> colors = new ArrayList<Integer>(n);    int pairs = 0;    for (int i = 0; i < n; i++) {       if (!colors.contains(ar[i])) {            colors.add(ar[i]);        } else {            pairs++;            colors.remove(ar[i]);        }    }    System.out.println(pairs);    return pairs;}private static final Scanner scanner = new Scanner(System.in);public static void main(String[] args) throws IOException {    // n is the size of the array    // sample n input: 9    int n = scanner.nextInt();    scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");    int[] ar = new int[n];    //sample arItems input: 10 20 20 10 10 30 50 10 20    String[] arItems = scanner.nextLine().split(" ");    scanner.skip("(\r\n|[\n\r\u2028\u2029\u0085])?");    for (int i = 0; i < n; i++) {        int arItem = Integer.parseInt(arItems[i]);        ar[i] = arItem;    }    int result = sockMerchant(n, ar);    scanner.close();}我得到的錯誤是：Exception in thread "main" java.lang.IndexOutOfBoundsException: Index 20 out-of-bounds for length 2    at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:64)    at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:70)    at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:248)    at java.base/java.util.Objects.checkIndex(Objects.java:372)    at java.base/java.util.ArrayList.remove(ArrayList.java:517)    at Solution.sockMerchant(Solution.java:21)    at Solution.main(Solution.java:48)