This week's giveaway is in the Android forum.
We're giving away four copies of Android Security Essentials Live Lessons and have Godfrey Nolan on-line!
See this thread for details.
The moose likes Programmer Certification (SCJP/OCPJP) and the fly likes Inquisition Question Big Moose Saloon
  Search | Java FAQ | Recent Topics | Flagged Topics | Hot Topics | Zero Replies
Register / Login


Win a copy of Android Security Essentials Live Lessons this week in the Android forum!
JavaRanch » Java Forums » Certification » Programmer Certification (SCJP/OCPJP)
Bookmark "Inquisition Question" Watch "Inquisition Question" New topic
Author

Inquisition Question

Neha Daga
Ranch Hand

Joined: Oct 30, 2009
Posts: 504


Choose all that apply:
A) Compiles with warning
B) A runtime exception occurs
C) Compiles without warning
D) Only one test object is added, Other one is considered duplicate
E) TreeSet can only accept objects of type test.

Answer is : B,C & E

my question is why will there be a runtime exception.


SCJP 1.6 96%
Ankit Garg
Sheriff

Joined: Aug 03, 2008
Posts: 9291
    
  17

Hint: The class test implements Comparator and not Comparable...


SCJP 6 | SCWCD 5 | Javaranch SCJP FAQ | SCWCD Links
Neha Daga
Ranch Hand

Joined: Oct 30, 2009
Posts: 504
so that means, Comparator interface can only be implemented by a class separate from the class whose instances are to be sort.

am I right?
G Venu
Greenhorn

Joined: Mar 30, 2009
Posts: 5
TreeSet collection object created with default constructor takes elements that implement Comparable interface only.
When the code tries to insert elements that violate this constraint, ClassCastException will be thrown.

To me the code should not even compile.

http://java.sun.com/javase/7/docs/api/java/util/TreeSet.html#TreeSet()
Neha Daga
Ranch Hand

Joined: Oct 30, 2009
Posts: 504
G Venu wrote:TreeSet collection takes elements that implement Comparable interface only. When the code tries to insert elements that violate this constraint, ClassCastException will be thrown.



Got this point.


To me the code should not even compile.


the code will compile because objects added are mutually comparable i.e they both are Test objects.
It would throw ClassCastException if you add a Test and say a Integer.
G Venu
Greenhorn

Joined: Mar 30, 2009
Posts: 5
Agreed. exception should be seen at runtime only

replacing with should fix the issue. (the code does not make much sense doing this though)
Phungsuk Wangdu
Ranch Hand

Joined: Nov 04, 2009
Posts: 114
thanks venu and neha you just cleared a lot of my doubts
 
I agree. Here's the link: http://aspose.com/file-tools
 
subject: Inquisition Question
 
Similar Threads
Comparator and Compatable Query
Mock Exam Question
TreeSet & Comparator
comparator comparable
Comparable or Comparator