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Questions and Answers
What type of exception is an ArrayIndexOutOfBoundsException?
What type of exception is an ArrayIndexOutOfBoundsException?
- Checked Exception
- Error
- Unchecked Exception (correct)
- IOException
Which of the following exceptions is a checked exception?
Which of the following exceptions is a checked exception?
- IOException (correct)
- NoSuchMethodException
- StringIndexOutOfBoundsException
- ArithmeticException
What is the purpose of the finally block in a try-catch block?
What is the purpose of the finally block in a try-catch block?
- To throw exceptions
- To release resources (correct)
- To catch exceptions
- To specify requirements
What is the Throwable class in Java?
What is the Throwable class in Java?
What happens to the local variables in a try block after an exception is thrown?
What happens to the local variables in a try block after an exception is thrown?
What is the difference between a checked and an unchecked exception?
What is the difference between a checked and an unchecked exception?
What type of exception is a NullPointerException?
What type of exception is a NullPointerException?
What is the purpose of the catch block in a try-catch block?
What is the purpose of the catch block in a try-catch block?
What is the superclass of all errors and exceptions in Java?
What is the superclass of all errors and exceptions in Java?
What is the purpose of the Finally block in a Try-Catch-Finally statement?
What is the purpose of the Finally block in a Try-Catch-Finally statement?
What is the difference between checked and unchecked exceptions?
What is the difference between checked and unchecked exceptions?
What is the benefit of using a single Scanner object in a project?
What is the benefit of using a single Scanner object in a project?
What is the purpose of the Try block in a Try-Catch-Finally statement?
What is the purpose of the Try block in a Try-Catch-Finally statement?
What is an example of an exception that might occur in a program?
What is an example of an exception that might occur in a program?
What is the benefit of using exception handling in a program?
What is the benefit of using exception handling in a program?
What is the effect of using the final modifier with a class?
What is the effect of using the final modifier with a class?
What happens to the control after the last catch block is executed?
What happens to the control after the last catch block is executed?
What is the main difference between a try block and a try statement?
What is the main difference between a try block and a try statement?
What is the purpose of the finally block in a try-catch-finally statement?
What is the purpose of the finally block in a try-catch-finally statement?
What is the difference between the throw and throws keywords?
What is the difference between the throw and throws keywords?
What is the characteristic of a checked exception?
What is the characteristic of a checked exception?
What is the best practice for catching exceptions?
What is the best practice for catching exceptions?
What is the purpose of the try-with-resources statement?
What is the purpose of the try-with-resources statement?
What is an example of an unchecked exception?
What is an example of an unchecked exception?
What is the primary goal of professional programmers when it comes to exception handling?
What is the primary goal of professional programmers when it comes to exception handling?
What type of exception should a programmer typically not catch?
What type of exception should a programmer typically not catch?
What is the purpose of using a TRY…CATCH…FINALLY block?
What is the purpose of using a TRY…CATCH…FINALLY block?
What is the relationship between the Throwable class and the Exception and Error classes?
What is the relationship between the Throwable class and the Exception and Error classes?
Why is it important to handle exceptions in a program?
Why is it important to handle exceptions in a program?
What happens when an exception is thrown in a TRY block?
What happens when an exception is thrown in a TRY block?
What is the main difference between a checked and an unchecked exception?
What is the main difference between a checked and an unchecked exception?
What is the correct order of execution in a TRY…CATCH…FINALLY block?
What is the correct order of execution in a TRY…CATCH…FINALLY block?
What is the main purpose of using the try-catch block in exception handling?
What is the main purpose of using the try-catch block in exception handling?
Which of the following is a characteristic of a checked exception?
Which of the following is a characteristic of a checked exception?
What is the purpose of the Throwable class in Java's exception hierarchy?
What is the purpose of the Throwable class in Java's exception hierarchy?
What happens when an exception is thrown in a try block and not caught by any catch block?
What happens when an exception is thrown in a try block and not caught by any catch block?
What is the benefit of using a finally block in a try-catch block?
What is the benefit of using a finally block in a try-catch block?
Which of the following is an example of a runtime exception?
Which of the following is an example of a runtime exception?
What is the primary difference between a checked and an unchecked exception?
What is the primary difference between a checked and an unchecked exception?
Why is it a good practice to handle exceptions as close to the source of the exception as possible?
Why is it a good practice to handle exceptions as close to the source of the exception as possible?
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Study Notes
Exceptions
- An exception is a strange event that can potentially make a program fail.
- Exceptions can be handled using TRY…CATCH…FINALLY.
Exceptions Hierarchy
- Throwable: supertype of all exceptions and errors in Java.
- Three subclasses of Throwable:
- Error: system errors, cannot be caught (e.g. OutOfMemoryError).
- Exception: base class for all exceptions in Java, programmers throw and catch exceptions.
- RuntimeException: a runtime programming error, cannot be thrown and caught (e.g. NullPointerException).
Types of Exceptions
- Checked Exceptions: typically caused by conditions that are not under the control of the program, compiler enforces special requirements (e.g. IOException, ClassNotFoundException).
- Unchecked Exceptions: all exception types that are direct or indirect subclasses of RuntimeException, avoidable by bulletproofing your code (e.g. ArrayIndexOutOfBoundsExceptions, ArithmeticExceptions).
Exception Handling
- Try block: specifies the requirement syntax, where the exception can occur.
- Catch block: handles the exception, can rethrow an exception.
- Finally block: always executes when the try block exits, typically used to release resources.
- Catch should be as close to the problem as possible, and place catch blocks from the specific to general.
Throws and Throw
- Throw: used to throw an exception for a method, cannot throw multiple exceptions.
- Throws: used to indicate what exception types may be thrown by a method, can declare multiple exceptions.
Best Practices
- Catch should be as close to the problem as possible.
- Place catch blocks from the specific to general.
- A catch block can rethrow an exception.
- Reuse existing exception classes where possible, but you can create new ones if needed.
- Only the first matching catch executes.
Final Modifier
- With variable: becomes constant.
- With method: cannot be overridden in subclasses.
- With class: cannot be sub-classed.
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