We sample with replacement, so it's possible to choose the same value twice.
Here are the 16 possible samples of size 2:

sample     x̄     
(1,1)     1.0
(1,2)     1.5
(1,3)     2.0
(1,4)     2.5
(2,1)     1.5
(2,2)     2.0
(2,3)     2.5
(2,4)     3.0
(3,1)     2.0
(3,2)     2.5
(3,3)     3.0
(3,4)     3.5
(4,1)     2.5
(4,2)     3.0
(4,3)     3.5
(4,4)     4.0

There are 7 possible sample means. We list each sample with its frequency,
which is the number of times it occurs in the list of 16 above:

   x̄     f   
  1.0    1    
  1.5    2    
  2.0    3    
  2.5    4    
  3.0    3    
  3.5    2    
  4.0    1    

Here's the histogram:




Edwin