用线性时间复杂度实现找出数组中出现一次的元素

public class fingNumber {
public static void main(String [] args){
int [] arr=new int[]{3,4,3,4,3,4,5,5,5,6,6,6,7,7,7,8,8,8,1};
findNumber(arr);
}

private static void findNumber(int[] arr) {
int a=0,b=0;
for(int i=0;i<arr.length;i++){
b=a&(b^arr[i]);
a=b|(a^arr[i]);
}
System.out.println(a);
}
}