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EXCEL ENGINEERING COLLEGE
(Autonomous)
COMPUTER SCIENCE AND ENGINEERING
III Semester
20CS302 – OBJECT ORIENTED PROGRAMMING
Regulations 2020
Question Bank with Answer Key
UNIT – III (APPLETS, EXCEPTION HANDLING AND I/O)
PART- A
Q.No Questions
Define Exception.
1  A Java exception is an object that finds an exceptional condition occurs from a piece of code.
 An exception object is created and thrown to the method from the code where an exception is found.
Recall the purpose of exception handling mechanism.
 The main purpose of exception handling mechanism is used to detect and report an “exceptional
circumstance” so that necessary action can be taken. It performs the following tasks
 Find the problem(Hit the exception)
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 Inform that an error occurred(throw the exception).
 Receive the error information(Catch the exception)
 Take corrective actions(Handle the exception)

What are the types of exceptions?
 There are two types of exceptions
3  Predefined Exceptions-The Exceptions which are predefined are calledpredefined exceptions
 Userdefined Exceptions- The Exceptions which are defined by the userare called userdefined exceptions

How the exception handling is managed?
 Java exception handling is managed via five keywords.
 try
4  catch
 throw
 throws and
 finally

Write down the general form of an exception-handling block.
 The general form of an exception-handling blocktry
{
// block of code to monitor for errors
}
catch (ExceptionType1 exOb)

5 {
// exception handler for ExceptionType1

}
catch (ExceptionType2 exOb)

{
// exception handler for ExceptionType2

, }
// ...
finally
{
// block of code to be executed after try block ends
}

List out the two subclasses under Throwable class.
 Throwable is a superclass for all exception types. Thus, Throwable is at topof the exception hierarchy.
 There are two subclasses under Throwable class.
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 Exception
 Error

What is an Error?
 The another subclass is by Error, which defines exceptions that are notexpected to be caught under
normal circumstances by your program.
7  Exceptions of type Error are used by the Java run-time system to indicateerrors having to do with the run-
time environment, itself.
 Eg: Stack overflow is an example of such an error.

Identify the situation where we need to use multiple catchclauses.
 In some situation, more than one exception can occur by a single piece of code.
 To handle this situation, we can use two or more catch clauses, each catching a different type of exception.
8 When an exception is thrown, each catch block is executed in order, and the first one whose type matches
that exception is executed.
 After one catch block executes, the others are bypassed, and continues after the try/catch block.

Why we need to use nested try statements.
 The try statement can be nested. That is, a try statement can be inside the block of another try.
 Each time a try statement is entered, the context of that exception is pushed on the stack.
 If an inner try statement does not have a catch handler for a particular exception, the stack is unwound
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and the next try statement’s catch handlers are inspected for a match.
 This continues until one of the catch statements succeeds, or until all of the nested try statements are
exhausted. If no catch statement matches, then the Java run-time system will handle the exception.

Write down the use of throws clause.
 Using throws clause, We can list the types of exceptions that a method might throw.
10  The exceptions which are thrown in a method might be using throws clause. If they are not, a compile-time
error will result.

Give the use of finally clause.
 Finally creates a block of code that is to be executed after a try/catch block has completed its execution.
 The finally block will execute if an exception is thrown or not thrown.
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 The finally clause is optional.
 Each try block requires either one catch or a finally clause

Define Unchecked Exception.
 These are the exceptions that are not checked at compiled time.
12  In C++, all exceptions are unchecked, so it is not forced by the compiler to either handle or specify the
exception.
 It is up to the programmers to be civilized, and specify or catch the exceptions.