Test invariants by using assertions.
1. The correct answer is C.
The ++ operator increments the value of x to 1 before the condition is evaluated. Note that changing values of variables or objects in assertions is discouraged since there's no guarantee that assertions would be enabled when the program runs.
2. The correct answer is A.
You can disable assertion at the command-line. The other statements are false.
3. The correct answer is B.
The command:
java -esa -ea:com.example MainClass
Enables assertions in system classes and classes in the com.example package.
4. The correct answer is D.
There's nothing wrong with the program, the method isValid() returns false, which makes the program to throw an AssertionError at runtime.
5. The correct answer is B.
assert false : "Assertion is false"
Behaves in a similar way to:
throw new AssertionError("Asssertion is false");
When assertions are enabled.