QuipoIn

Java HashMap

Which of the following statements about HashMap is correct?

A. It allows duplicate keys 

B. It allows one null key and multiple null values 

C. It maintains insertion order 

D. It is synchronized by default 

What happens when two keys in a HashMap have the same hash code?

A. One key is removed 

B. It throws an exception 

C. A collision occurs, handled by a linked list / tree 

D. Both keys are stored without issue 

Which data structure is used internally by HashMap?

A. ArrayList 

B. Hashtable 

C. Array + LinkedList / Tree (for collisions) 

D. TreeMap 

Which of the following is NOT true about HashMap?

A. It is not synchronized by default 

B. It provides constant-time performance for get/put in average case 

C. It maintains keys in ascending order 

D. It allows one null key 

What is the default initial capacity of a HashMap?

A. 8

B. 16

C. 32

D. 64