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Submitted by c-admin on Tue, 05/28/2019 - 22:15

QID:

165

Type:

Multiple Choice Question

Category:

Java Programmer I

Tags:

Looping Constructs

Question:

Which of the following code snippets will compile without any errors?
(Assume that the statement int x = 0; exists prior to the statements below.)

Select 3 options

A. while (false) { x=3; }
B. if (false) { x=3; }
C. do{ x = 3; } while(false);
D. for( int i = 0; i< 0; i++) x = 3;

Answer and Explanation (Click to expand)

Answer:

B, C, D

Explanation:

while (false) { x=3; } is a compile-time error because the statement x=3; is not reachable; Similarly, for( int i = 0; false; i++) x = 3; is also a compile time error because x= 3 is unreachable.

In if(false){ x=3; }, although the body of the condition is unreachable, this is not an error because the JLS explicitly defines this as an exception to the rule. It allows this construct to support optimizations through the conditional compilation.

For example,

if(DEBUG){ System.out.println("beginning task 1"); }

Here, the DEBUG variable can be set to false in the code while generating the production version of the class file, which will allow the compiler to optimize the code by removing the whole if statement entirely from the class file.

Q&A Set:

Set 17

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