SCJA Mock Exam Question on the Switch Statement

[Stephen Davies]

During my revision towards my SCJA,I came uponm this uCertify Question in a mock exam.

Q. You work as[sic] a computer faculty. You want to take the tutorial about enumeration types in Java. You write the following code:

enum Colors{red,blue,green}
 
class  Stringtest {
 
 public static void main (String args[]){
 
      Colors col = Colors.blue;
 
   switch(col) {
 
      case red:System.out.print("danger");
 
      default:System.out.print("Default");
 
      case blue:System.out.print("sky is the limit");
 
      case green:System.out.print("healthy wealthy and wise");
 
      }
   }
 }

What will be the output when you try to comile and run the code?

My answer: C: It will generate a compile-time error

-my answer is based on the fact that an argument to a switch statement must be compatible with type int (as they explain themselevs in the answer review)

uCertify answer: A: it will display the sky is the limit healthy wealthy and wise.


Is it some twisted logic that they reach their answer (like if the switch argument is not compatible the statement isrun anyway), or is their answer wrong outright. I appreciate some advice here!

Thanks in advance

Steve

[greg fuentes]

The code will call the enum and get blue as the value, the switch/case block will fall through to the entry for "blue" and output the text given. Then, because there is no break: statement the code will continue through the next case and then exit.

[greg fuentes]

BTW, after stepping into this code with the Netbeans IDE, i can confidently say that the way it is written, the switch function sees the value "blue" and jumps right to it, bypassing the "case:red..." and the "default:..." entries. Additionally when i moved the default line to the end of the switch code block, it also outputs "default" as well. Apparently the DEFAULT entry needs to be the very last entry or it will be ignored if bypassed initially.
hope this helps. Actually watching code step through its lines using the F7 key is a great learning tool in Netbeans.

[patrick avery]

Stephen: you said "-my answer is based on the fact that an argument to a switch statement must be compatible with type int (as they explain themselevs in the answer review)"

This used to be 100% correct, but the latest versions of Java also allow enums along with primitives compatible with type int in switch statements

Good Luck, Pat Avery

[Stephen Davies]

Thanks Greg & Patrick.

I was more asking of the switch compatibility with enums, I am aware of the break statement etc. Yes you're right as of Java 5 enums can be passed to a switch block.I looked it up in my JAVA Desktop reference (5th ed.) O'Reilly. Its an interesting change, but for the best (if your into switch statements!) :roll:

I'm an eclipse man myself, but using a mac, day to day I love TextMate
[ September 14, 2008: Message edited by: Stephen Davies ]