The questions in this Java quiz are on the topics covered in the Java - Flow Control section of the site. The table below lists the
lessons, a description of the lesson content and the the quiz question number range.
Lesson Summary
Click on a lesson in the table to go to that lesson for a refresher on the topics for that lesson.
| Flow Control Lessons |
Description |
Question Range |
| Lesson 1 - Exception Overview | We begin our studies of Java exceptions by looking at the Java exception hierarchy and the various classes within it. | 1 - 4 |
| Lesson 2 - Handling Exceptions | Now we know what the Java exception hierarchy looks like and the classes involved its time to start handling exceptions which may occur within our code. | 5 - 11 |
| Lesson 3 - Declaring Exceptions | In this lesson we learn how to use the throw keyword which allows to throw exceptions from within our methods. We also investigate how to declare exceptions using the throws keyword. | 12 - 18 |
| Lesson 4 - Creating Our Own Exceptions | In this lesson we learn how to create our own exceptions and use them in our code. | |
| Lesson 5 - Using Assertions | For this lesson we learn about the Assertion mechanism and how to write and then enable any assertion code within our programs. | 19 - 25 |
Java Quiz
The quiz below tests your knowledge of the material learnt in the Java - Flow Control section of the site.
Question 1 : Which class is at the top of the inheritance hierarchy
- The <code>Throwable</code> class is at the top of the inheritance hierarchy.
Question 2 : What type of exceptions do we have to declare in our code?
- We have to declare Checked exceptions in our code or the compiler complains.
Question 3 : What type of exception classes can we as programmers do nothing about?
- The <code>Error</code> class and its subclasses handle error situations from within the JVM itself and so are outside our control as programmers.
Question 4 : What do we have to do with checked exceptions?
- We have to declare checked exceptions.
Question 5 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try {
int a = 5 / 0;
}
System.out.println("We can just continue on now.");
}
}
- We will get a compiler error as we cannot have a <code>try</code> without a <code>catch</code> or a <code>finally</code>.
Question 6 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try { int a = 5 / 0; System.out.print("A."); }
catch (Exception ex) { System.out.print("B."); }
System.out.print("C.");
}
}
- As soon as the exception occurs in the <code>try</code> block it is caught in the <code>catch</code> block which prints B. then the program continues and prints
out C. so the answer is B.C.
Question 7 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try { int a = 5 / 0; }
System.out.print("A.");
catch (Exception ex) { System.out.print("B."); }
System.out.print("C.");
}
}
- A <code>catch</code> block must immediately follow a <code>try</code> block and there is a statement between them so we get a compiler error.
Question 8 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try { int a = 5 / 0; }
finally { System.out.print("A."); }
System.out.print("B.");
}
}
- The <code>finally</code> block runs and prints A. and then the program crashes so we get A. followed by the runtime error output
Question 9 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try { int a = 5 / 0; }
finally { System.out.print("A."); }
catch (Exception ex) { System.out.print("B."); }
System.out.print("C.");
}
}
- The <code>finally</code> block must come immediately after any <code>catch</code> blocks and not before.
Question 10 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try { int a = 5 / 0; }
catch (Exception ex) { System.out.print("B."); }
System.out.print("C.");
finally { System.out.print("A."); }
}
}
- There can be no other code between the <code>try</code>, <code>catch</code> and <code>finally</code> blocks so we get a compiler error.
Question 11 : What would be output from the following code snippet?
public class DivideByZero {
public static void main(String[] args) {
try { int a = 5 / 0; }
catch (Exception ex) { System.out.print("B."); }
catch (ArithmeticException ex) { System.out.print("C."); }
finally { System.out.print("A."); }
System.out.print("D.");
}
}
- We get a compiler error. When using multiple <code>catch</code> blocks, they need to be ordered from the most specific to the most generic.
Question 12 : How do we declare exceptions in our methods?
- We declare exceptions in our methods using the <code>throws</code> keyword.
Question 13 : What exceptional conditions can we throw from within our code?
- We can <code>throw</code> any exceptional conditions from within our code, so all of the above.
Question 14 : What does the compiler demand we do with checked exceptions?
- The compiler demands that we handle or declare <em>checked exceptions</em>.
Question 15 : What happens when an exception occurs in a method that declares but doesn't handle the exception?
- When an exception occurs in a method that declares but doesn't handle the exception, the exception propogates up the stack
Question 16 : An overriding method can throw any Error or RuntimeException exceptions, whether these are declared in the overridden method or not.
- The above statement is <code>true</code>.
Question 17 : An overriding method can throw any new checked exceptions or any checked exceptions that are higher up the inheritance tree than those declared in the overridden method.
- An <em>overriding</em> method MUST NOT throw any new <em>checked exceptions</em> or any <em>checked exceptions</em> that are higher up the inheritance tree than those declared in the <em>overridden</em> method, so the above statement is <code>false</code>.
Question 18 : An overriding method can throw any checked exceptionss that are lower down the inheritance tree than those declared in the overridden method but this isn't mandatory.
- The above statement is <code>true</code>.
Question 19 : Assertions should be used to validate command-line arguments.
- We certainly can use assertions to validate command-line arguments. The problem with this approach is that would have to run the code everytime using the -ea option to ensure assertions run the validation.
Question 20 : What should we use to validate arguments to a public method.
- We have no control over a public interface and so we should NOT use assertions. We should use exceptions for validating arguments to a public method.
Question 21 : Assertions should never be used that cause side-effects?
- This is <code>true</code> as assertions should never be used that cause side-effects. Imagine changing a value when assertions are turned on, we are reliant on code being run using the <code>-ea</code> option to get the values changed.
Question 22 : In what situation would we use assert false;?
- We would use <code>assert false;</code> for cases that are never supposed to happen, such as a <code>switch default</code> that should never be reached.
Question 23 : Is the following code snippet an appropriate use of assertions?
public class A {
public void methodA(int a) {
assert (a > 0)
// more code
}
}
- The above code snippet is not an appropriate use of assertions as we have no control over usage of a public interface. Use exceptions to validate input to a <code>public</code> method.
Question 24 : Is the following code snippet an appropriate use of assertions?
public class A {
private void methodA(int a) {
assert (a > 0)
// more code
}
}
- The above code snippet is an appropriate use of assertions as we should have complete control over usage of a <code>private</code> method.
Question 25 : Assertions have no 'hit on performance?
- Assertion code leaves no footprint and is just ignored when a class is run without the <code>-ea</code> option, so there is no 'hit' on performance.
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What's Next?
In the next quiz we test knowledge of the java API.
