```
//I sorted the numbers first and then found if any two adjacent numbers exist in the sorted array.
import java.util.Arrays;
public class Solution {
public int findDuplicate(int[] nums) {
Arrays.sort(nums);
for(int i=0;i<nums.length;i++)
{
if(nums[i]==nums[i+1])
return nums[i];
}
return 0;
}
}
```