This week's book giveaway is in the JavaScript forum.
We're giving away four copies of Svelte and Sapper in Action and have Mark Volkmann on-line!
See this thread for details.
Win a copy of Svelte and Sapper in Action this week in the JavaScript 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
  • Ron McLeod
  • Paul Clapham
  • Bear Bibeault
  • Junilu Lacar
Sheriffs:
  • Jeanne Boyarsky
  • Tim Cooke
  • Henry Wong
Saloon Keepers:
  • Tim Moores
  • Stephan van Hulst
  • Tim Holloway
  • salvin francis
  • Frits Walraven
Bartenders:
  • Scott Selikoff
  • Piet Souris
  • Carey Brown

mock question about "case"

 
Ranch Hand
Posts: 186
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator
Chapter 5 Question 13. Given:
1. class Ring {
2. final static int x2 = 7;
3. final static Integer x4 = 8;
4. public static void main(String[] args) {
5. Integer x1 = 5;
6. String s = "a";
7. if(x1 < 9) s += "b";
8. switch(x1) {
9. case 5: s += "c";
10. case x2: s += "d";
11. case x4: s += "e";
12. }
13. System.out.println(s);
14. }
15. }
What is the result?
A. abc
B. abcde
C. Compilation fails due only to an error on line 7.
D. Compilation fails due only to an error on line 8.
E. Compilation fails due only to an error on line 10.
F. Compilation fails due only to an error on line 11.
G. Compilation fails due to errors on multiple lines.
============================
Answer:
F is correct. A switch statement requires its case expressions to be constants, and wrapper variables (even final static ones) aren�t considered constants. The rest of the code is correct.
A, B, C, D, E, and G are incorrect based on the above. (Objective 2.1)

========================
my question is...x2 is final static, how would it go through? (just because it is not a wrapper class?)
 
Java Cowboy
Posts: 16084
88
Android Scala IntelliJ IDE Spring Java
  • Mark post as helpful
  • send pies
  • Quote
  • Report post to moderator

Originally posted by adam lui:
my question is...x2 is final static, how would it go through? (just because it is not a wrapper class?)


Yes, that's exactly the reason.

Some more info: The Java Language Specification, section 14.11 says that case expressions must be constant expressions, as explained in section 15.28. An instance of a wrapper class is not a constant expression. (In practice it is constant because the wrapper classes are immutable, but the Java compiler doesn't know that the wrapper classes are immutable).
[ September 05, 2007: Message edited by: Jesper Young ]
 
this is supposed to be a surprise, but it smells like a tiny ad:
Thread Boost feature
https://coderanch.com/t/674455/Thread-Boost-feature
    Bookmark Topic Watch Topic
  • New Topic