HashSet vs LinkedHashSet

Question

What is the difference between them? I know that

A LinkedHashSet is an ordered version of HashSet that maintains a doubly-linked List across all el

Answer 1

I suggest you to use LinkedHashSet most of the time, because it has better performance overall):

1. Predictable iteration order LinkedHashSet (Oracle)
2. LinkedHashSet is more expensive for insertions than HashSet;
3. In general slightly better performance than HashMap, because the most of the time we use Set structures for iterating.

Performance tests:

------------- TreeSet -------------
 size       add  contains   iterate
   10       746       173        89
  100       501       264        68
 1000       714       410        69
10000      1975       552        69
------------- HashSet -------------
 size       add  contains   iterate
   10       308        91        94
  100       178        75        73
 1000       216       110        72
10000       711       215       100
---------- LinkedHashSet ----------
 size       add  contains   iterate
   10       350        65        83
  100       270        74        55
 1000       303       111        54
10000      1615       256        58

You can see source test page here: The Final Performance Testing Example