Most Frequently asked Collection Interview Question

How HashMap works internally in Java

Difference between ArrayList and Vector

How HashSet works internally in Java

Difference between Comparable and Comparator

Hashtable vs HashMap


Comparator vs Comparable                                                             

ArrayList vs Vector                                                                              

HashMap vs ConcurrentHashMap

HashSet vs TreeSet 

Fail Fast Iterator vs Fail Safe Iterator

Iterator vs Enumeration

 ==  vs equals method

HashMap vs Hashtable

Top 10 Interview Questions :

Top 10 HashSet Interview Questions

Internal Working

Internal working of HashSet  
HashMap internal working