Win a copy of Learning Regular Expressions this week in the General Computing forum!
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
programming forums Java Mobile Certification Databases Caching Books Engineering Micro Controllers OS Languages Paradigms IDEs Build Tools Frameworks Application Servers Open Source This Site Careers Other all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Liutauras Vilda
  • Campbell Ritchie
  • Tim Cooke
  • Bear Bibeault
  • Devaka Cooray
Sheriffs:
  • Jeanne Boyarsky
  • Knute Snortum
  • Junilu Lacar
Saloon Keepers:
  • Tim Moores
  • Ganesh Patekar
  • Stephan van Hulst
  • Pete Letkeman
  • Carey Brown
Bartenders:
  • Tim Holloway
  • Ron McLeod
  • Vijitha Kumara

HashSet Magic  RSS feed

 
Ranch Hand
Posts: 30
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Apparently, the unsorted unordered HashSet (pg. 562 K&B) comes with a bit of magical sorting after all. The initial capacity of a HashSet is 16 so adding more numbers ruins the magic. http://download.oracle.com/javase/6/docs/api/java/util/HashSet.html

After reading up on hashing, I realized that this must be caused by the hashing algorithm doing (key % tableSize) which produces pseudo-sorting up to initial capacity. Am I correct?



[15]
[14, 15]
[13, 14, 15]
[12, 13, 14, 15]
[11, 12, 13, 14, 15]
[10, 11, 12, 13, 14, 15]
[9, 10, 11, 12, 13, 14, 15]
[8, 9, 10, 11, 12, 13, 14, 15]
[7, 8, 9, 10, 11, 12, 13, 14, 15]
[6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

[0]
[0, 1]
[0, 1, 2]
[0, 1, 2, 3]
[0, 1, 2, 3, 4]
[0, 1, 2, 3, 4, 5]
[0, 1, 2, 3, 4, 5, 6]
[0, 1, 2, 3, 4, 5, 6, 7]
[0, 1, 2, 3, 4, 5, 6, 7, 8]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

 
Ranch Hand
Posts: 5575
Eclipse IDE Java Windows XP
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Cole Tarbet wrote: I realized that this must be caused by the hashing algorithm doing (key % tableSize) which produces pseudo-sorting up to initial capacity. Am I correct?


You are right! from HashSet[again it is nothing but HashMap] source code :
 
Don't get me started about those stupid light bulbs.
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!