This solution is not efficient but very easy to understand.

```
public class Solution {
public int[] nextGreaterElement(int[] findNums, int[] nums) {
int[] result=new int[findNums.length];
// go through each element in findNums
for(int i=0;i<findNums.length;i++)
{
for(int j=0;j<nums.length;j++)
{ // if we find one findNums element in second array, set result[i]=-1
if(findNums[i]==nums[j])
{
result[i]=-1;
}// if we already find the element in second array, and we can find a next greater number, set the value to the greater value;
if(result[i]==-1&&nums[j]>findNums[i])
{
result[i]=nums[j];
}
}
}
return result;
}
}
```