Part 1
Java interview questions on exception handling covered in this post:
What are the exceptions?
- Exception is an event, can be occurred during the execution of the program
that disrupts the normal flow of the program.
- You can say an Exception is an abnormal event that can be occurred during
the execution of the program.
- Exception can stop the execution of the program if not handled.
What is the difference between exception and error?
|
|
Error |
Exception |
|
1. |
Error is an invalid condition. |
An exception is an abnormal condition. |
|
2. |
An error cannot be handled. |
An exception can be handled. |
|
3. |
Error stops your program immediately. |
If you handle exceptions then your program may execute
smoothly. |
|
4. |
An error can occur only run time but not compile time. |
An exception can occur compile time and run time. |
|
5. |
Error belongs to java.lang.Error |
Exeception belongs to java.lang.Exception. |
|
6. |
e.g. OutOfMemoryError |
e.g. NullPointerException, FileNotFoundException. |
 
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What is the difference between checked exceptions and unchecked
exceptions?
|
|
Checked Exception |
Unchecked Exception |
|
1. |
Checked Exceptions can occur at Compile time. |
Unchecked Exceptions can occur at run time. |
|
2. |
If you don’t handle checked exceptions then your code will not
compile. You will get a compile-time error. |
If you don’t handle unchecked exceptions you will get an exception
at run time but your program will be compiled. |
|
3. |
Checked Exceptions extends Throwable and Error but except
RuntimeException. |
Unchecked Exceptions extends RuntimeException. |
|
4. |
Examples :
IOException, SQLException, FileNotFoundEx ception |
Examples:
NullPointerException, ArithmeticException,
ArrayIndexOutofBoundException |
How many types we can handle the exception?
-
We can handle exceptions in two ways.
1.
Using try and catch block.
2.
Using throws keyword.
-
Please refer to the below example to try-catch block.
|
package simplifiedjava.crackedInterview;
public
class
Aeroplane {
public
void
setLocation(String locationName) {
try
{
if(locationName.equals(null)) {
throw
new
NullPointerException();
}
}catch(NullPointerException e) {
e.printStackTrace();
}
}
} |
- Please refer to the below example for the throws keyword.
|
package
simplifiedjava.crackedInterview; public class Aeroplane {
public
void
setLocation(String locationName)throws
NullPointerException {
if(locationName.equals(null)) {
throw
new
NullPointerException();
}
}
} |
Which is the parent class of the Exception hierarchy?
- Parent Class of Exception is Throwable.
What is the difference between the throw and throws keyword?
|
|
Throw |
Throws |
|
1. |
Throw keyword can be used to throw an exception manually or
explicitly. |
Throws keyword can be used to declare the list of exceptions. |
|
2. |
Throw can be declared inside a method. |
Throws can be declared in method definition followed by the
parameter list. |
|
3. |
Only one Exception can be thrown with the throw keyword. |
Multiple Exceptions can be declared with the throws keyword. |
|
4. |
The checked exception cannot throw with the throw keyword. |
Checked and Unchecked exceptions can declare with the throws
keyword. |
What is exception propagation?
- An Exception is thrown from the current method and if it is not handled
then it drops to the previous method. If that exception is not handled in
the previous method as well then it drops to the previous method and so on.
If you never handle that exception then that exception reached to main
method or base method which is called exception propagation.
- Please refer to the below diagram of exception propagation.
|
Current Method |
Exception occurred in this function and it is not handled. |
|
m4() |
Exception not handled in current method so dropped in method
m4(). |
|
m3() |
Exception not handled in m4() method so dropped in method m3(). |
|
m2() |
Exception not handled in m3() method so dropped in method m2(). |
|
m1() |
Exception not handled in m2() method so dropped in method m1(). |
|
main() or base() |
Exception not handled in m1() so dropped in main() method and the
program terminates abruptly. |
Can you explain the exception hierarchy?
-
Compile Time Exception or Checked Exception.
1.
FileNotFoundException.
2.
ClassNotFoundException.
3.
NoSuchFieldException.
4.
NoSuchMethodException.
5.
InvalidClassException.
6.
InvalidObjectException.
7.
CloneNotSupportedException.
8.
InterruptedException.
-
Runtime Exception or Unchecked Exception.
1.
NullPointerException.
2.
ArithmeticException.
3.
ClassCastException.
4.
IndexOutOfBoundException.
5.
ArrayIndexOutOfBoundException.
6.
StringIndexOutOfBoundException.
7.
IllegalStateException
8.
IllegalMonitorStateException
-
Error.
1.
OutOfMemoryError.
2.
StackOverFlowError.
3.
IOError.
4.
AssertionError.
What is a multi-catch block? In which java version it has been
introduced?
- In one catch block we can handle multiple exceptions is called a
multi-catch block.
- Pipe Operator “|” can be used to segregate multiple exceptions.
- Multi catch block has been introduced in Java 7.
- Please refer to the below example for a multi-catch block.
|
package simplifiedjava.crackedInterview; public class Aeroplane {
public
void
setLocation(String locationName){
try
{
if(locationName.equals(null)) {
throw
new
NullPointerException();
}
}catch(NullPointerException | ArithmeticException e) {
e.printStackTrace();
}
}
} |
What is the role of the printStackTrace() method? This method belongs
to which class?
- printStackTrace() method is used to diagnosing the exceptions.
- This method points out exactly where the exception occurred. It will print
the function name and line number as well.
- printStackTrace() method belongs to the Throwable class which is the super
parent class of the Exception hierarchy.
- For reference to the printStackTrace() method you can refer to the previous
example.
- Java interview questions and answers all MNC - Click here
- Basic core java interview questions and answers for freshers - Click here
- Core java interview questions for 3 years experience - Click here
- Core java interview questions and answers for 3-5 years exp - Click here
- Core java interview questions and Answers for 5 - 7 Years exp - Click here
- Basic Java Interview Questions and Answers - Click here
- Java interview questions and answers on oops - Click here
- Java interview questions and answers on Strings - Click here
- Java interview questions on exception handling - Click here
- Interview questions on multithreading in java for experienced - Click here
- Interview questions on serialization in java for experienced - Click here
- Interview questions on inner class in java for experienced - Click here
- Interview questions on Collections in java for experienced - Click here
11. Can we create custom exception class. If yes then what are the steps to create customer exception class.
12. Can you identify which try, catch and finally block combination is valid.
13. Can we declare empty catch block.
14. Can you explain why NullPointerException occurred and how to handle it?
15. Can you explain why ClassCastException occurred and how to handle it?
16. Can you explain why OutofMemoryError occurred and how to handle it?
17. Can you explain why StackOverflowError occurred and how to handle it?
18. Can you explain why ClassNotFoundError occurred and how to handle it?
19. Can you explain why ExceptionInInitializerError occurred and how to handle it?
20.what's the difference between stackoverflowerror and outofmemoryerror in java
|
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