LonelyInteger.java

public class LonelyInteger {
    static int findLonelyInteger(int[] nums) {
        int x = nums[0];
        for (int i = 1; i < nums.length; i++) {
            x ^= nums[i];
        }
        return x;
    }

    public static void main(String[] args) {
        int[] nums = {0, 0, 1, 2, 1};
        System.out.println(findLonelyInteger(nums));
    }
}