Win a copy of Microservices in Action this week in the Web Services 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:
  • Campbell Ritchie
  • Bear Bibeault
  • Devaka Cooray
  • Liutauras Vilda
  • Jeanne Boyarsky
Sheriffs:
  • Knute Snortum
  • Junilu Lacar
  • paul wheaton
Saloon Keepers:
  • Ganesh Patekar
  • Frits Walraven
  • Tim Moores
  • Ron McLeod
  • Carey Brown
Bartenders:
  • Stephan van Hulst
  • salvin francis
  • Tim Holloway

Generic Question  RSS feed

 
Ranch Hand
Posts: 209
Java Tomcat Server
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
[b]
[/b]
Can some one make me explain why this is not compiling.The compiler is telling me that Parameter is not within Bounds......

Also not understanding then how this is working ??
[b]
[/b]

Please Help me ??

Examples would be really appreciated !!

Can someone please help me with an example of my 2 Questions ??
 
Sheriff
Posts: 9643
42
Android Google Web Toolkit Hibernate IntelliJ IDE Java Spring
  • Likes 2
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

In this case you are declaring a new K with your method declaration. Basically the code is equivalent to this code

Now here M might be resolved to something not compatible with Number, like lets say String. But Test class can only have a type which is a Number. So you'll have to bound M to a number.


Here first of all the type declaration in the method is useless. So we'll strip it out first

Now the return type would clearly work. As for the parameter, since you are using a wildcard syntax, so compile would be able to maintain type safety here. Lets actually put some code into the class to see how

Basically you can't make changes to s variable based on its type as the type is not known. So even though ? super K seems to be breaking the bounds of K, it will still result in type safe code which is the goal of generics...
 
Sagar Shroff
Ranch Hand
Posts: 209
Java Tomcat Server
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Thanks Ankit !!
 
It is sorta covered in the JavaRanch Style Guide.
  • Post Reply Bookmark Topic Watch Topic
  • New Topic
Boost this thread!