• 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 Pie Elite all forums
this forum made possible by our volunteer staff, including ...
Marshals:
  • Campbell Ritchie
  • Tim Cooke
  • Devaka Cooray
  • Ron McLeod
  • Jeanne Boyarsky
Sheriffs:
  • Liutauras Vilda
  • paul wheaton
  • Junilu Lacar
Saloon Keepers:
  • Tim Moores
  • Stephan van Hulst
  • Piet Souris
  • Carey Brown
  • Tim Holloway
Bartenders:
  • Martijn Verburg
  • Frits Walraven
  • Himai Minh

Collections

 
Ranch Hand
Posts: 30
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Hi all
Please Solve my query about HashMap and TreeMap.
We Can Store null key in HashMap but we can't store
null key in TreeMap It is giving runtime exception.
Why this is so?
 
Java Cowboy
Posts: 16084
88
Android Scala IntelliJ IDE Spring Java
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
TreeMap sorts its elements by key. The map cannot be sorted properly if one of the keys is 'null' - so 'null' is not allowed as a key.
 
shri Sonparote
Ranch Hand
Posts: 30
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Thank you
 
shri Sonparote
Ranch Hand
Posts: 30
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Thank you I have one more doubt

Why set.add("sds"); throw java.lang.UnsupportedOperationException
 
Ranch Hand
Posts: 377
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator

Originally posted by shri Sonparote:
Why set.add("sds"); throw java.lang.UnsupportedOperationException



Have a look at the API documentation of TreeMap.keySet().
 
shri Sonparote
Ranch Hand
Posts: 30
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Thank You
 
Humans and their filthy friendship brings nothing but trouble. My only solace is this tiny ad:
the value of filler advertising in 2021
https://coderanch.com/t/730886/filler-advertising
reply
    Bookmark Topic Watch Topic
  • New Topic