Topic 8.4: Handling Exceptions - Create and invoke a method that throws an exception

Question 1

What is the purpose of the throw statement?

Answer 1

This statement is used to indicate exceptional conditions or errors during program execution by explicitly throwing an exception.

Question 2

This statement is used to indicate exceptional conditions or errors during program execution by explicitly throwing an exception.

Answer 2

What is the purpose of the throw statement?

Question 3

Give an example of a method that throws an exception explicitly.

Answer 3

Example:

public void validateInput(String input) 
{
    if (input == null) {
        throw new IllegalArgumentException("Input cannot be null");
    }
    // Perform other validation logic
}

Question 4

Syntax:

accessModifier returnType methodName(parameters) throws ExceptionType1, ExceptionType2, ...

Answer 4

What is the syntax for a method signature with exception throwing?

Question 5

What is the syntax for throwing an exception?

Answer 5

Syntax:

throw exceptionInstance;

Question 6

This is achieved by including the ‘throws’ keyword followed by the exception type(s) in the method declaration.

Answer 6

How do you indicate the possibility of throwing exceptions in a method signature in Java?

Question 7

What is the syntax for catching and handling exceptions using catch blocks?

Answer 7

Syntax:

try {
    // Code that may throw an exception
} catch (ExceptionType1 e1) {
    // Handle exception of type ExceptionType1
} catch (ExceptionType2 e2) {
    // Handle exception of type ExceptionType2
} catch (ExceptionType3 e3) {
    // Handle exception of type ExceptionType3
}

Question 8

Should catch blocks for more specific exception types be placed before catch blocks for more general exception types? Why?

Answer 8

Yes, catch blocks for more specific exception types should be placed before catch blocks for more general exception types. This ensures that specific exceptions are handled appropriately before more general catch blocks are reached.

Question 9

What can happen if catch blocks for more specific exception types are placed after catch blocks for more general exception types?

Answer 9

If catch blocks for more specific exception types are placed after catch blocks for more general exception types, the specific catch blocks will never be reached, and the more general catch blocks will handle the exceptions, resulting in incorrect or undesirable handling of specific exceptions.

Question 10

Why is the order of catch blocks important?

Answer 10

The order of catch blocks is important because the first catch block that matches the exception type is executed.

Question 11

How do you create and throw exceptions in Java?

Answer 11

This is achieved by using the ‘throw’ keyword followed by an instance of an exception class.

Question 12

Syntax:

try {
    // Code that may throw an exception
} catch (ExceptionType1 e1) {
    // Handle exception of type ExceptionType1
} catch (ExceptionType2 e2) {
    // Handle exception of type ExceptionType2
} catch (ExceptionType3 e3) {
    // Handle exception of type ExceptionType3
}

Answer 12

What is the syntax for catching and handling exceptions using catch blocks?

Question 13

Example of this situation:

public void readFile(String fileName) throws FileNotFoundException

Answer 13

Give an example of a method that can potentially throw a FileNotFoundException.

Question 14

Syntax:

throw exceptionInstance;

Answer 14

What is the syntax for throwing an exception?

Question 15

This is achieved by using the ‘throw’ keyword followed by an instance of an exception class.

Answer 15

How do you create and throw exceptions in Java?

Question 16

Example:

public void divideNumbers(String dividend, String divisor) 
{
    try {
        int result = Integer.parseInt(dividend) / Integer.parseInt(divisor);
        System.out.println("Result: " + result);
    } catch (ArithmeticException e) {
        System.err.println("Error: Division by zero");
    } catch (NumberFormatException e) {
        System.err.println("Error: Invalid number format");
    }
}

Answer 16

Give an example of a method that catches and handles the ArithmeticException and NumberFormatException separately.

Question 17

Do unchecked exceptions require explicit declaration in the method signature or explicit handling?

Answer 17

No, unchecked exceptions, such as RuntimeException and its subclasses, do not need to be declared in the method signature or explicitly handled.

Question 18

These are exceptions that must be declared using the ‘throws’ clause or handled explicitly within the method.

Answer 18

What are checked exceptions in Java?

Question 19

What are checked exceptions in Java?

Answer 19

These are exceptions that must be declared using the ‘throws’ clause or handled explicitly within the method.

Question 20

In this situation the caller is responsible for either handling the exception using try-catch blocks or declaring it in its own method signature using the ‘throws’ keyword.

Answer 20

What is the responsibility of the caller when invoking a method that throws a checked exception?

Question 21

How do you indicate the possibility of throwing exceptions in a method signature in Java?

Answer 21

This is achieved by including the ‘throws’ keyword followed by the exception type(s) in the method declaration.

Question 22

Example:

public void validateInput(String input) 
{
    if (input == null) {
        throw new IllegalArgumentException("Input cannot be null");
    }
    // Perform other validation logic
}

Answer 22

Give an example of a method that throws an exception explicitly.

Question 23

Give an example of a method that can potentially throw a FileNotFoundException.

Answer 23

Example of this situation:

public void readFile(String fileName) throws FileNotFoundException

Question 24

What is the purpose of a catch block?

Answer 24

This is used to handle and respond to specific types of exceptions that occur within a try block.

Question 25

What is the order in which catch blocks are evaluated when multiple catch blocks are present?

Answer 25

Catch blocks are evaluated sequentially from top to bottom.

Question 26

What is the responsibility of the caller when invoking a method that throws a checked exception?

Answer 26

In this situation the caller is responsible for either handling the exception using try-catch blocks or declaring it in its own method signature using the ‘throws’ keyword.

Question 27

Give an example of a method that catches and handles the ArithmeticException and NumberFormatException separately.

Answer 27

Example:

public void divideNumbers(String dividend, String divisor) 
{
    try {
        int result = Integer.parseInt(dividend) / Integer.parseInt(divisor);
        System.out.println("Result: " + result);
    } catch (ArithmeticException e) {
        System.err.println("Error: Division by zero");
    } catch (NumberFormatException e) {
        System.err.println("Error: Invalid number format");
    }
}

Question 28

This is used to handle and respond to specific types of exceptions that occur within a try block.

Answer 28

What is the purpose of a catch block?

Question 29

What is the syntax for a method signature with exception throwing?

Answer 29

Syntax:

accessModifier returnType methodName(parameters) throws ExceptionType1, ExceptionType2, ...