Topic 8.2: Handling Exceptions - Create a try-catch block and determine how exceptions alter normal program flow Flashcards
This exception is a subclass of IOException and is specifically thrown when a file is requested but cannot be found during an I/O operation.
How is the FileNotFoundException different from the IOException in Java?
What is the importance of providing meaningful error messages when throwing exceptions?
Providing descriptive and meaningful error messages helps developers diagnose and fix issues quickly by understanding what went wrong.
When is the throw keyword typically used?
This keyword is typically used within methods to raise an exception when a specific condition is met or when an error occurs that the method cannot handle itself.
These blocks in Java allow you to handle multiple exceptions in a single catch block by specifying the exception types separated by vertical bars (|) in the catch parameter.
This feature was introduced in Java SE 7 and helps reduce code duplication and improves code readability when you want to handle multiple exception types in a similar way.
How do multi-catch blocks in Java allow you to handle multiple exceptions in a single catch block?
This class is the superclass of all errors in Java.
Errors represent severe issues that may not be recoverable by application code. Examples include StackOverflowError and OutOfMemoryError.
What is the purpose of the java.lang.Error class in the exception hierarchy?
This exception occurs in Java when a method that converts a string to a numeric type encounters an inappropriate format in the input string.
When does the NumberFormatException exception occur in Java?
What should be considered when using multiple catch blocks effectively?
Order catch blocks from specific to general to ensure proper handling of exceptions.
What is the purpose of using multiple catch blocks in Java exception handling?
These allow handling various exceptions differently for improved application robustness.
This exception is thrown in Java when an arithmetic operation produces an exceptional condition, such as division by zero.
What does the ArithmeticException exception indicate, and when is it thrown in Java?
What is the purpose of the java.lang.Error class in the exception hierarchy?
This class is the superclass of all errors in Java.
Errors represent severe issues that may not be recoverable by application code. Examples include StackOverflowError and OutOfMemoryError.
When this occurs, the program’s flow of control jumps to the nearest enclosing try-catch block or terminates if there is no appropriate handler.
How does an exception alter the flow of control in a program?
These allow developers to define application-specific exceptional conditions and provide more meaningful information to the calling code about the error that occurred.
They enhance the clarity and understanding of exceptional situations and enable developers to handle errors in a more specific and context-aware manner.
Why are custom exceptions useful?
Give an example of handling a checked exception
Example:
public void handleFile() {
try {
readFile();
} catch (IOException e) {
// Handle the exception here
}
}
What does the NullPointerException exception indicate, and when is it thrown in Java?
This exception is thrown in Java when a program attempts to access a member (a field or method) of an object that is currently null.
This occurs when an object reference is pointing to nothing (null) and an operation is performed on it.
What happens if there is no matching catch block for an exception in the try block?
If there is no matching catch block, the control jumps to the nearest finally block (if present) before propagating the exception.
These allow handling various exceptions differently for improved application robustness.
What is the purpose of using multiple catch blocks in Java exception handling?
What is the syntax of the try-catch block in Java?
Basic Syntax:
try {
// Code that may throw an exception
} catch (ExceptionType1 e1) {
// Exception handling code for ExceptionType1
} catch (ExceptionType2 e2) {
// Exception handling code for ExceptionType2
}
// More catch blocks as needed
How do multi-catch blocks in Java allow you to handle multiple exceptions in a single catch block?
These blocks in Java allow you to handle multiple exceptions in a single catch block by specifying the exception types separated by vertical bars (|) in the catch parameter.
This feature was introduced in Java SE 7 and helps reduce code duplication and improves code readability when you want to handle multiple exception types in a similar way.
what is a similarity between Checked and Unchecked Exceptions
Both types of exceptions will propagate up the call stack, searching for an appropriate catch block.
If no catch block is found, both checked and unchecked exceptions will result in program termination.
These in Java are abnormal conditions or errors that disrupt the normal flow of the program when something unexpected happens during execution.
What is the role of exceptions in a Java program?
How are exceptions handled using try-catch blocks?
The code that may throw an exception is placed within the try block.
If an exception occurs, it is caught and handled by the corresponding catch block, ensuring controlled handling of exceptional situations.
What happens if you create a new exception object but do not use the ‘throw’ keyword to throw it?
If you create a new exception object without using ‘throw,’ the exception will not be propagated or caught, having no effect on the program’s flow of execution.
This is thrown when an attempt is made to cast an object to a type that is not compatible with the object’s actual type.
What is the purpose of the ClassCastException in Java?
What caution should be exercised when catching exceptions in a program?
Avoid swallowing exceptions without taking any action, as this can hide important issues and make it difficult to identify problems in the code.
In what order are catch blocks evaluated and executed when an exception is thrown?
Catch blocks are evaluated in order of appearance, and only the first matching catch block is executed.
This keyword is typically used within methods to raise an exception when a specific condition is met or when an error occurs that the method cannot handle itself.
When is the throw keyword typically used?
How does a catch block determine which exception to handle?
When an exception is thrown within the try block, the Java runtime searches for a matching catch block that can handle the specific type of exception. It checks each catch block in order of appearance to find the first one whose exception type matches the thrown exception’s type.
The exception type is determined by the class of the thrown exception or one of its subclasses.
In catch blocks, you write code that defines how to handle the caught exception gracefully. This may include:
- displaying an error message
- logging the exception
- attempting to recover from the exceptional situation
- or taking appropriate corrective actions.
The purpose of catch blocks is to handle exceptions properly to ensure the program doesn’t crash unexpectedly and provides useful information to the user or developer when an exceptional condition occurs.
What is the purpose of catch blocks in exception handling?
Is the ‘throw’ keyword required to propagate an exception to a catch block in Java?
Yes, the ‘throw’ keyword is necessary to explicitly throw an exception, causing it to propagate up the call stack to find a suitable catch block.
How is the FileNotFoundException different from the IOException in Java?
This exception is a subclass of IOException and is specifically thrown when a file is requested but cannot be found during an I/O operation.
What happens if an exception is not caught and handled in Java?
If this is not caught and handled, it propagates up the call stack, and if there is no appropriate catch block, the program terminates abruptly, displaying the exception’s details as a “stack trace.”
What is the purpose of the java.lang.RuntimeException class in Java?
This class is a subclass of java.lang.Exception and represents unchecked exceptions in Java.
Unchecked exceptions do not need to be explicitly caught or declared, and they typically occur due to programming errors or unexpected conditions during runtime.
Examples include NullPointerException, ArithmeticException, and ArrayIndexOutOfBoundsException.
What happens when the throw statement is executed?
When the throw statement is executed:
- the normal flow of the program is interrupted
- and the control jumps to the nearest matching catch block that can handle the thrown exception.
- If no matching catch block is found, the control moves up the call stack until a suitable handler is found or the program terminates.
What happens if an exception is caught by a catch block within a try-catch construct?
After executing the code in the catch block, the program continues with the statements following the try-catch block, maintaining the program’s flow of execution.
what are 4 key points on un-checked exceptions
Key points include:
- These exceptions are exceptions that do not need to be caught or explicitly declared using the throws keyword.
- These exceptions are subclasses of java.lang.RuntimeException
- These are usually caused by programming errors, improper use of language features, or unexpected conditions during runtime.
- These are not required to be handled at compile-time. Instead, they are allowed to propagate up the call stack until they are caught and handled by an appropriate catch block or result in program termination.
This is used for exception handling in Java, enclosing code that might throw exceptions and providing specific handlers to deal with those exceptions.
What is the purpose of a try-catch block in Java?
Key points include:
- These exceptions are exceptions that do not need to be caught or explicitly declared using the throws keyword.
- These exceptions are subclasses of java.lang.RuntimeException
- These are usually caused by programming errors, improper use of language features, or unexpected conditions during runtime.
- These are not required to be handled at compile-time. Instead, they are allowed to propagate up the call stack until they are caught and handled by an appropriate catch block or result in program termination.
what are 4 key points on un-checked exceptions
How do you create custom exceptions in Java
To create custom exceptions in Java:
- Create a new class that extends either Exception (for checked exceptions) or RuntimeException (for unchecked exceptions).
- Define constructors for your custom exception class, which can accept a message or additional information to explain the exceptional condition.
- Within your code, when a specific condition requires raising the exception, create an instance of your custom exception using the new keyword and throw it using the throw keyword.
What is the purpose of the exception handling mechanism in Java?
This mechanism allows developers to gracefully recover from exceptions or handle exceptional situations in a controlled manner.
This is used for cleanup operations and contains code that always executes, regardless of exceptions.
What is the purpose of the finally block in Java exception handling?
This class is a subclass of java.lang.Exception and represents unchecked exceptions in Java.
Unchecked exceptions do not need to be explicitly caught or declared, and they typically occur due to programming errors or unexpected conditions during runtime.
Examples include NullPointerException, ArithmeticException, and ArrayIndexOutOfBoundsException.
What is the purpose of the java.lang.RuntimeException class in Java?
Why is proper exception handling essential for a Java program?
Properly handled exceptions:
- maintain program stability
- prevent abrupt termination
- allow the program to recover from errors
in turn the program becomes more user-friendly.
What is the purpose of the ClassCastException in Java?
This is thrown when an attempt is made to cast an object to a type that is not compatible with the object’s actual type.
This exception is thrown in Java when a program attempts to access a member (a field or method) of an object that is currently null.
This occurs when an object reference is pointing to nothing (null) and an operation is performed on it.
What does the NullPointerException exception indicate, and when is it thrown in Java?
If this is not caught and handled, it propagates up the call stack, and if there is no appropriate catch block, the program terminates abruptly, displaying the exception’s details as a “stack trace.”
What happens if an exception is not caught and handled in Java?
What is the purpose of the IOException class in Java?
This class is the superclass of all exceptions related to input-output (I/O) operations in Java. It is thrown when an I/O operation fails or is interrupted.
what are 4 key points on checked exceptions
Key points include:
- These are exceptions that must be either caught or declared in the method signature using the throws keyword.
- These exceptions are subclasses of java.lang.Exception (but not java.lang.RuntimeException)
- These are typically used to represent recoverable errors or exceptional conditions that the application can handle.
- Checked exceptions are checked by the compiler, meaning the compiler enforces the requirement for the code to either catch the exception or declare it using the throws keyword. If a method can throw a checked exception, the calling code must handle the exception.
Key points include:
- These are exceptions that must be either caught or declared in the method signature using the throws keyword.
- These exceptions are subclasses of java.lang.Exception (but not java.lang.RuntimeException)
- These are typically used to represent recoverable errors or exceptional conditions that the application can handle.
- Checked exceptions are checked by the compiler, meaning the compiler enforces the requirement for the code to either catch the exception or declare it using the throws keyword. If a method can throw a checked exception, the calling code must handle the exception.
what are 4 key points on checked exceptions
This class is the superclass of all exceptions in Java.
Exceptions represent exceptional conditions that can be handled by application code. Unlike errors, exceptions are intended to be caught and handled.
What is the java.lang.Exception class, and how does it differ from java.lang.Error?
What is the purpose of a try-catch block in Java?
This is used for exception handling in Java, enclosing code that might throw exceptions and providing specific handlers to deal with those exceptions.
What is the purpose of the finally block in Java exception handling?
This is used for cleanup operations and contains code that always executes, regardless of exceptions.
This class is the superclass of all exceptions related to input-output (I/O) operations in Java. It is thrown when an I/O operation fails or is interrupted.
What is the purpose of the IOException class in Java?
What is the root class of the Java exception hierarchy, and what methods does it provide?
The root class of the Java exception hierarchy is java.lang.Throwable.
It provides methods to get information about the exception, such as getMessage() and printStackTrace().
Does the finally block alter the flow of exception propagation?
No, the finally block does not alter the flow of exception propagation; it executes after catch blocks and before propagating the exception.
What is the role of exceptions in a Java program?
These in Java are abnormal conditions or errors that disrupt the normal flow of the program when something unexpected happens during execution.
How does the try-catch block handle exceptions?
When an exception occurs within the try block, Java searches for a matching catch block that corresponds to the type of exception.
The first matching catch block’s code is executed, providing a controlled response to the exceptional condition.
How should exceptions be handled in a program?
Exceptions should be handled at the appropriate level where the problem can be effectively addressed or where there is enough context to take appropriate action.
When is the ArrayIndexOutOfBoundsException exception thrown in Java?
This exception is thrown in Java when an invalid index is used to access an array element.
This can happen when using a negative index or an index greater than or equal to the array’s length.
Provoide an example of creating a custom exception class
Example:
public class CustomException extends Exception {
public CustomException() {
super("This is a custom checked exception.");
}
public CustomException(String message) {
super(message);
}
}
Why should exceptions not be used for flow control in a program?
Exceptions are designed for handling exceptional and unexpected conditions, not for controlling the regular flow of execution. Using exceptions for flow control can lead to inefficient and hard-to-maintain code.
provide an example of declaring a checked exception in a method signature
example:
public void readFile() throws IOException {
// Code that may throw IOException
}
What is the purpose of catch blocks in exception handling?
In catch blocks, you write code that defines how to handle the caught exception gracefully. This may include:
- displaying an error message
- logging the exception
- attempting to recover from the exceptional situation
- or taking appropriate corrective actions.
The purpose of catch blocks is to handle exceptions properly to ensure the program doesn’t crash unexpectedly and provides useful information to the user or developer when an exceptional condition occurs.
How does an exception alter the flow of control in a program?
When this occurs, the program’s flow of control jumps to the nearest enclosing try-catch block or terminates if there is no appropriate handler.
Example:
public void methodB() {
try {
// Some code that may throw exceptions
} catch (IOException | NullPointerException | IllegalArgumentException e) {
// Handle all three exception types in a single catch block
System.out.println("Exception caught: " + e.getMessage());
}
}
provide an example of a multi-catch block
This mechanism allows developers to gracefully recover from exceptions or handle exceptional situations in a controlled manner.
What is the purpose of the exception handling mechanism in Java?
What does the ArithmeticException exception indicate, and when is it thrown in Java?
This exception is thrown in Java when an arithmetic operation produces an exceptional condition, such as division by zero.
Why are custom exceptions useful?
These allow developers to define application-specific exceptional conditions and provide more meaningful information to the calling code about the error that occurred.
They enhance the clarity and understanding of exceptional situations and enable developers to handle errors in a more specific and context-aware manner.
When the throw statement is executed:
- the normal flow of the program is interrupted
- and the control jumps to the nearest matching catch block that can handle the thrown exception.
- If no matching catch block is found, the control moves up the call stack until a suitable handler is found or the program terminates.
What happens when the throw statement is executed?
This keyword is used to explicitly throw an exception, indicating that something exceptional has happened in the code.
What is the purpose of the throw keyword in Java?
What is the purpose of the throw keyword in Java?
This keyword is used to explicitly throw an exception, indicating that something exceptional has happened in the code.
provide an example of a multi-catch block
Example:
public void methodB() {
try {
// Some code that may throw exceptions
} catch (IOException | NullPointerException | IllegalArgumentException e) {
// Handle all three exception types in a single catch block
System.out.println("Exception caught: " + e.getMessage());
}
}
What is the java.lang.Exception class, and how does it differ from java.lang.Error?
This class is the superclass of all exceptions in Java.
Exceptions represent exceptional conditions that can be handled by application code. Unlike errors, exceptions are intended to be caught and handled.
Example:
public void handleFile() {
try {
readFile();
} catch (IOException e) {
// Handle the exception here
}
}
Give an example of handling a checked exception
How should you choose between checked and unchecked exceptions in Java?
Use checked exceptions for recoverable errors that require handling at compile time. Use unchecked exceptions for unrecoverable errors caused by programming mistakes.
Why is logging exceptions with detailed stack traces essential for debugging?
Logging exceptions with stack traces allows developers to trace the sequence of method calls and identify the root cause of the problem during debugging.
To create custom exceptions in Java:
- Create a new class that extends either Exception (for checked exceptions) or RuntimeException (for unchecked exceptions).
- Define constructors for your custom exception class, which can accept a message or additional information to explain the exceptional condition.
- Within your code, when a specific condition requires raising the exception, create an instance of your custom exception using the new keyword and throw it using the throw keyword.
How do you create custom exceptions in Java
When does the NumberFormatException exception occur in Java?
This exception occurs in Java when a method that converts a string to a numeric type encounters an inappropriate format in the input string.
This exception is thrown in Java when an invalid index is used to access an array element.
This can happen when using a negative index or an index greater than or equal to the array’s length.
When is the ArrayIndexOutOfBoundsException exception thrown in Java?
example:
public void readFile() throws IOException {
// Code that may throw IOException
}
provide an example of declaring a checked exception in a method signature
