java-exceptions

Exception Handling

The goal of this exercise is to practise:

• Creating custom exceptions
• Handling exceptions

For the exercises below, we've provided the starter project above.

📌 Exceptions

Question 1

Is the following code legal?

try {

} finally {

}

Question 2

What exception types can be caught by the following handler?

catch (Exception e) {
    
}

What is wrong with using this type of exception handler?

Question 3

Is there anything wrong with the following exception handler as written? Will this code compile?

try {

} catch (Exception e) {

} catch (ArithmeticException a) {

}

Question 4

int[] A; 
A[0] = 0;

The above code produces (choose 1):

• an error
• a checked exception
• an unchecked exception
• a compile error
• no exception

Question 5

The JVM starts running your program, but the JVM can't find the Java platform classes. (The Java platform classes reside in classes.zip or rt.jar.)

What happens (choose 1):

• an error
• a checked exception
• an unchecked exception
• a compile error
• no exception

📌 Custom Exceptions

Create a custom (checked) exception class called FilenameException.

Create a class called FileExtension with the following methods:

• boolean check(String filename)
• Map<String, int> map(List<String> filenames)

The check method should:

• return true when the file extension is .java
• return false when the file extension is not .java
• throw a FilenameException when the file name is null or an empty string.

The map method should:

• check each provided file's extension and map the returned value as 1 if true or 0 if false
• map -1 when an exception occurs

Example

For the following list of file names: Arrays.asList("App.java", "App.txt", null, "App.md"), the map method should return a map with the following entries:

{"App.java", 1},
{"App.txt", 0},
{null, -1},
{"App.md", 0}

✅ Verify Your Implementation

To verify that your code works as expected, run the provided unit tests.

In your terminal, ensure that you are in the java-exceptions folder, then run the following command:

./mvnw clean test

If you are on Windows, run this command instead:

mvnw clean test

Your implementation is correct when all tests pass.

ℹ️ Notes

If you want to experiment with the provided application in the App.java file, you can run the following command from the terminal:

./mvnw -q clean compile exec:java

Or on Windows:

```bat
mvnw -q clean compile exec:java