array sum2 challenge

Hi,

i am trying  below challenge

http://codingbat.com/prob/p190968

i tried as below

public int sum2(int[] nums) {

int numsSum[]=new int[4];

if(nums.length>=2)
return nums[0]+nums[1];

//  else (nums.length==1)
 // return nums[0];
  return 0;
}

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Expected	Run		
sum2({1, 2, 3}) → 3	3	OK	    
sum2({1, 1}) → 2	2	OK	    
sum2({1, 1, 1, 1}) → 2	2	OK	    
sum2({1, 2}) → 3	3	OK	    
sum2({1}) → 1	0	X	    
sum2({}) → 0	0	OK	    
sum2({4, 5, 6}) → 9	9	OK	    
sum2({4}) → 4	0	X	    
other tests
OK	    

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i failed few tests. How to fix and improve my code. please advise