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  • Question
  • Which three statements are true?

    1. Assertion checking is typically enabled when a program is deployed.
    2. It is never appropriate to write code to handle failure of an assert statement.
    3. Assertion checking is typically enabled during program development and testing.
    4. Assertion checking can be selectively enabled or disabled on a per-package basis, but not on a per-class basis.
    5. Assertion checking can be selectively enabled or disabled on both a per-package basis and a per-class basis.


  • Options
  • A. 1, 2 and 4
  • B. 2, 3 and 5
  • C. 3, 4 and 5
  • D. 1, 2 and 5

  • Correct Answer
  • 2, 3 and 5 

    Explanation
    (1) is wrong. It's just not true.

    (2) is correct. You're never supposed to handle an assertion failure.

    (3) is correct. Assertions let you test your assumptions during development, but the assertion code?in effect?evaporates when the program is deployed, leaving behind no overhead or debugging code to track down and remove.

    (4) is wrong. See the explanation for (5) below.

    (5) is correct. Assertion checking can be selectively enabled or disabled on a per-package basis. Note that the package default assertion status determines the assertion status for classes initialized in the future that belong to the named package or any of its "subpackages".

    The assertion status can be set for a named top-level class and any nested classes contained therein. This setting takes precedence over the class loader's default assertion status, and over any applicable per-package default. If the named class is not a top-level class, the change of status will have no effect on the actual assertion status of any class.


    Assertions problems


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    • 1. Which of the following statements is true?

    • Options
    • A. If assertions are compiled into a source file, and if no flags are included at runtime, assertions will execute by default.
    • B. As of Java version 1.4, assertion statements are compiled by default.
    • C. With the proper use of runtime arguments, it is possible to instruct the VM to disable assertions for a certain class, and to enable assertions for a certain package, at the same time.
    • D. When evaluating command-line arguments, the VM gives -ea flags precedence over -da flags.
    • Discuss
    • 2. Which of the following statements is true?

    • Options
    • A. In an assert statement, the expression after the colon ( : ) can be any Java expression.
    • B. If a switch block has no default, adding an assert default is considered appropriate.
    • C. In an assert statement, if the expression after the colon ( : ) does not have a value, the assert's error message will be empty.
    • D. It is appropriate to handle assertion failures using a catch clause.
    • Discuss
    • 3. Which two can be used to create a new Thread?

      1. Extend java.lang.Thread and override the run() method.
      2. Extend java.lang.Runnable and override the start() method.
      3. Implement java.lang.Thread and implement the run() method.
      4. Implement java.lang.Runnable and implement the run() method.
      5. Implement java.lang.Thread and implement the start() method.

    • Options
    • A. 1 and 2
    • B. 2 and 3
    • C. 1 and 4
    • D. 3 and 4
    • Discuss
    • 4. Which statement is true?

    • Options
    • A. A static method cannot be synchronized.
    • B. If a class has synchronized code, multiple threads can still access the nonsynchronized code.
    • C. Variables can be protected from concurrent access problems by marking them with the synchronized keyword.
    • D. When a thread sleeps, it releases its locks.
    • Discuss
    • 5. Which statement is true?

    • Options
    • A. The notifyAll() method must be called from a synchronized context.
    • B. To call wait(), an object must own the lock on the thread.
    • C. The notify() method is defined in class java.lang.Thread.
    • D. The notify() method causes a thread to immediately release its locks.
    • Discuss
    • 6. Which statement is true?

    • Options
    • A. Assertions can be enabled or disabled on a class-by-class basis.
    • B. Conditional compilation is used to allow tested classes to run at full speed.
    • C. Assertions are appropriate for checking the validity of arguments in a method.
    • D. The programmer can choose to execute a return statement or to throw an exception if an assertion fails.
    • Discuss
    • 7. Which of the following statements is true?

    • Options
    • A. It is sometimes good practice to throw an AssertionError explicitly.
    • B. Private getter() and setter() methods should not use assertions to verify arguments.
    • C. If an AssertionError is thrown in a try-catch block, the finally block will be bypassed.
    • D. It is proper to handle assertion statement failures using a catch (AssertionException ae) block.
    • Discuss
    • 8. Which statement is true about assertions in the Java programming language?

    • Options
    • A. Assertion expressions should not contain side effects.
    • B. Assertion expression values can be any primitive type.
    • C. Assertions should be used for enforcing preconditions on public methods.
    • D. An AssertionError thrown as a result of a failed assertion should always be handled by the enclosing method.
    • Discuss


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