数组的计数,该如何解决

数组的计数
已知两个整型数组A和B，A的长度是100，数组内储存了100个不重复的整数，数组B的长度是99，从数组A内随机取出99个不重复的整数，储存在数级B内，求：在数组A内，但不在数组B内的那个整数

[解决办法]

Java code

public static void main(String[] args) {        List<Integer> A = new ArrayList<Integer>();        List<Integer> B = new ArrayList<Integer>();        for (int i = 0; i < 100; i++) {            A.add(i);            if(i == 99){                break;            }            B.add(i);        }                for (int i = 0; i < B.size(); i++) {            A.remove(B.get(i));        }        int result = A.get(0);        System.out.println(result);            }
[解决办法]
Java code
public class Demo {        private  int[] A = new int[100];    private  int[] B = new int[99];    private int random =0;        private void initA(){        for(int i = 0; i < 100; i++)            A[i] = i;    }        private void getBFromA(){        Random r=new Random();        random = r.nextInt(99);        for(int i = 0; i < random; i++)            B[i] = A[i];        for(int j = random; j < 99; j++)            B[j] = A[j+1];    }        public static void main(String[] args) {        Demo d = new Demo();        d.initA();        d.getBFromA();        for(int i:d.A)            System.out.print(i + " ");        System.out.println();        for(int i:d.B)            System.out.print(i + " ");        System.out.println();        System.out.println("在A不在B:"+d.A[d.random]);    }}