assertions

[matt love]

from Sierra and Bates.

class Hotel {
 static void doStuff(int x) {
 assert (x < 0) : "hotel";
 }
 }
 public class Motel13 extends Hotel {
 public static void main(String[] args) {
 doStuff(-5);
 int y = 0;
 assert (y < 0) : "motel";
 } }

Which of the following invocations will run without exception? (Choose all that apply.)
A. java Motel13
B. java -ea Motel13
C. java -da:Hotel Motel13
D. java -da:Motel13 Motel13
E. java -ea -da:Hotel Motel13
F. java -ea -da:Motel13 Motel13

Answer (for Objective 2.3):
A, C, D, and F are correct. When assertions are enabled, the Motel13 class will throw
an AssertionError, the Hotel class will not. Invocations A, C, and D do not enable
assertions for Motel13. F is correct because although assertions were enabled, the "–da"
switch selectively disabled assertions for the Motel13 class.
B and E are incorrect because assertions are enabled for Motel13.

Why is E not a correct answer? I read "java -ea -da:Hotel Motel13" as enable assertions for all classes and disable assertions for classes Hotel and Motel13.

Thanks.

Matt

[gurpeet singh]

matt love wrote:from Sierra and Bates.

class Hotel {
 static void doStuff(int x) {
 assert (x < 0) : "hotel";
 }
 }
 public class Motel13 extends Hotel {
 public static void main(String[] args) {
 doStuff(-5);
 int y = 0;
 assert (y < 0) : "motel";
 } }

Which of the following invocations will run without exception? (Choose all that apply.)
A. java Motel13
B. java -ea Motel13
C. java -da:Hotel Motel13
D. java -da:Motel13 Motel13
E. java -ea -da:Hotel Motel13
F. java -ea -da:Motel13 Motel13

Answer (for Objective 2.3):
A, C, D, and F are correct. When assertions are enabled, the Motel13 class will throw
an AssertionError, the Hotel class will not. Invocations A, C, and D do not enable
assertions for Motel13. F is correct because although assertions were enabled, the "–da"
switch selectively disabled assertions for the Motel13 class.
B and E are incorrect because assertions are enabled for Motel13.

Why is E not a correct answer? I read "java -ea -da:Hotel Motel13" as enable assertions for all classes and disable assertions for classes Hotel and Motel13.

Thanks.

Matt

java -ea -da:Hotel Motel13 is read as enable assertions for all the classes and disable assertions for the Hotel class and run the class file Motel13. the argument to the option -da are just Hotel. Motel13 is argument to java, i.e. it is the class file we are trying to run.

[matt love]

Great answer Gurpeet.

Thanks.

Matt