• 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
  • Jeanne Boyarsky
  • Ron McLeod
  • Paul Clapham
  • Liutauras Vilda
Sheriffs:
  • paul wheaton
  • Rob Spoor
  • Devaka Cooray
Saloon Keepers:
  • Stephan van Hulst
  • Tim Holloway
  • Carey Brown
  • Frits Walraven
  • Tim Moores
Bartenders:
  • Mikalai Zaikin

"? super Object" means what?

 
Greenhorn
Posts: 27
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Q1List <? super Object> list = new ArrayList <Object> ();

list.add(" "); // why this is allowed even when String is NOT Super
//type of Object?

list.add(new Object());

Q2
List <? extends Object> lst = new ArrayList <Object> ();
lst.add(new Object()); // not allowed. Why?
 
Ranch Hand
Posts: 324
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
As far as my idea is concern

in Q1 list can store any object whose Super class is Object.

in Q2 list can store any object who extends Object.
 
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
"Ajay C", please check your private messages. You can see them by clicking My Private Messages.
 
Ranch Hand
Posts: 37
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
Jesper what is the answer of this question please i also want to know
 
Greenhorn
Posts: 10
  • Mark post as helpful
  • send pies
    Number of slices to send:
    Optional 'thank-you' note:
  • Quote
  • Report post to moderator
When we use wild card notation with extends we cannot add ANYTHING . That is readonly . Now when you use wild card notation with super you can add to the collection . Since String is a Object you are allowed to add it.
reply
    Bookmark Topic Watch Topic
  • New Topic