Java OCA OCP Practice Question 2745

Question

What is the result of the following? 

Map<Integer, Integer> map = new HashMap<>(); 
map.put(1, 10); 
map.put(2, 20); 
map.put(3, null); 

map.merge(1, 3, (a,b) -> a + b); 
map.merge(3, 3, (a,b) -> a + b); 

System.out.println(map);
  • A. {1=10, 2=20}
  • B. {1=10, 2=20, 3=null}
  • C. {1=10, 2=20, 3=3}
  • D. {1=13, 2=20}
  • E. {1=13, 2=20, 3=null}
  • F. {1=13, 2=20, 3=3}
  • G. The code does not compile.
  • H. An exception is thrown.


F.

Note

The first call to merge() calls the mapping function and adds the two numbers to get 13.

It then updates the map.

The second call to merge() sees that the map currently has a null value for that key.

It does not call the mapping function but instead replaces it with the new value of 3.

Therefore choice F is correct.




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