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question about this code

 
Larry Lai
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Hi everyone,
why this code has a "?"
radius= (circleRadius>=0.0? circleRadius:0.0);


Thanks

Larry
 
Ken Cobbs
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Sorry about that blank post. Tyring to figure out how to make a post.
Any way, I believe that the '?' your asking about is like putting an 'if' statement in the middle of an expression. The example I see in 'Just Java2' 5th edition gives an example on page 131.
So
radius = ( circleRadius >= 0.0 ? circleRadius : 0.0 );
would mean that circleRadius would be evaluated if it 's >= 0.0 (true) and 0.0 if it's not >= 0.0(false).
My first post. Hope I didn't confuse 'ya.
Thanks,
Ken
 
Barry Gaunt
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Ken, you can delete the dead post via the edit icon.
The expression "boolean expression" ? "true alternative" : "false alternative" has been inherited from C/C++.
If "boolean expression" is true then the result of the expression is the result of the "true alternative" expression, else it is the result of the "false alternative" expression. The type of the result expression is the "widest" of the types of the two alternatives.
So true ? 9 : -1.0 will result in 9.0 (a double) being returned, and false ? 9 : -1.0 will result in -1.0 (also a double) being returned.
Its a bit tricky so look this up in your Java books because it can appear in Java Certification exams.
-Barry
 
Larry Lai
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Hey Barry,
Thanks a lot
I understand it now.
Larry
 
Ken Cobbs
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Thanks Barry,
I'll get this posting down(sometime).
 
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