HashSet in Java
  • HashSet it is based on HashTable 
  • Duplicate object not allowed in HashSet.
  • Insertion order is not preserved.
  • It is based on HashCode of object.
  • It allows Null Insertion.
  • Heterogeneous object are allowed
  • Internally implements Serializable Clonable Interface
  • Not implements RandomAccess Interface
  • HashSet is the best choice of frequent operation in the search operation

Linked HashSet

  • It is based on LinkedList+HashTable
  • preserved insertion oreder
  • duplicate object not allowed

Read more About Concurrent HashMap