LiquidJava Quiz

Test your knowledge about LiquidJava concepts including refinements, object state modeling and ghost variables!

1. Liquid types allow developers to catch bugs at:

   • Execution time
   • Compile time
   • Deployment time
   • Testing time

2. Liquid types can prevent which of the following bugs? (Select all that apply)

   • Array index out-of-bounds
   • Null pointer exceptions
   • Memory leaks
   • Division by zero

3. In LiquidJava, what integer values for x are allowed with this refinement? @Refinement("x > 0")

   • All values
   • All negative values
   • All non-negative values
   • All positive values

4. In LiquidJava, which of the following can be refined? (Select all that apply)

   • Variables
   • Parameters
   • Return values
   • Imports

5. In LiquidJava, which of the following is not a valid refinement?

   • @Refinement("x == 1 || x == -1")
   • @Refinement("x > 0")
   • @Refinement("x % 2 == 0")
   • @Refinement("x + 1")

6. In LiquidJava, to specify that a method should only be called when the object is in a certain state, we should use a:

   • @StateRefinement
   • @Refinement
   • @RefinementAlias
   • @RefinementPredicate

7. In LiquidJava, what does the following state refinement mean? @StateRefinement(from="!closed(this)", to="closed(this)")

   • The method can only be called when the object is closed and will leave it closed
   • The method can only be called when the object is open and will leave it open
   • The method can only be called when the object is not closed and will leave it closed
   • The method can be called in any state and will leave it closed

8. In LiquidJava, the @ExternalRefinementsFor annotation is used to:

   • Import refinements from external libraries
   • Define new refinements for an external class or interface
   • Export refinements to other modules
   • None of the above

9. In LiquidJava, a ghost variable is used to:

   • Store temporary data during the program execution
   • Model abstract properties of objects for verification purposes
   • Track memory usage of the program
   • Replace regular variables for better performance

10. In LiquidJava, which of the following refinements updates the ghost variable size?

    • @Refinement("size = 0")
    • @StateRefinement(from="size(this) > 0")
    • @Refinement("size == 0")
    • @StateRefinement(to="size(this) == size(old(this)) + 1")