Hashmap

Question 1

How does hashmap work

Answer 1

It stores key value pair and works based on the principle of hashing

Use hashing algorithm to generate hash code and compare with the hashcode() and equals() method

Question 2

What does hashmap store in the bucket (value)

Answer 2

It store both key and value

Question 3

What happens if two different. Hashmap key objects have same hashcode

Answer 3

Stored on same bucket in a linked list and the key equals method will help identify which entry in the list

Question 4

Hashmap, treemap and linkedhashmap

Answer 4

Hashmap - O (1) insertion and lookup. No order for keys
Treemap - O(log n) insertion and lookup . Keys are ordered in sorted manner.
Linkedhashmap - O(1) insertion and lookup. Keys are ordered by insertion order

Question 5

Iterate through a map

Answer 5

for (Map.Entry entry : map.entrySet())
System.out.println(“Key = “ + entry.getKey() +
“, Value = “ + entry.getValue());

Question 6

Sort by descending order

Answer 6

Collections.sort(result, (r1,r2) -> map.get(r1).equals(map.get(r2)) ?
r1.compareTo(r2) : map.get(r2).compareTo(map.get(r1)));