Top 10 Exception Handling interview questions in java

Exception handling is an important topic in Java and is often covered in job interviews for Java developers. Here are the top 10 exception handling interview questions, along with example answers:

1.What is an exception in Java?

An exception is an event that occurs during the execution of a program that disrupts the normal flow of instructions. Exceptions are typically used to handle unexpected conditions or errors that occur during the execution of a program.

2.What is the difference between checked and unchecked exceptions in Java?

Checked exceptions are those that are checked at compile-time and must be caught or declared in the method they are thrown from. Unchecked exceptions are those that are not checked at compile-time and do not need to be caught or declared. Examples of checked exceptions include IOException and SQLException, while examples of unchecked exceptions include NullPointerException and ArrayIndexOutOfBoundsException.

3.How do you handle exceptions in Java?

Exceptions can be handled in Java using try-catch blocks. A try block encloses the code that may throw an exception, and a catch block catches and handles the exception. The general syntax for a try-catch block is:

  try {
    // code that may throw an exception
} catch (ExceptionType ex) {
    // code to handle the exception
}

4.What is a finally block in Java?

A finally block is a block of code that is executed after the try and catch blocks, regardless of whether an exception is thrown or caught. The finally block is typically used to clean up resources, such as closing open files or connections.

try {
    // code that may throw an exception
} catch (ExceptionType ex) {
    // code to handle the exception
} finally {
    // code to clean up resources
}

5.What is a throw statement in Java?

A throw statement is used to explicitly throw an exception. The general syntax for a throw statement is:

throw new ExceptionType("exception message");

6.What is a throws clause in Java?

A throws clause is used to specify that a method may throw an exception. The general syntax for a throws clause is:

public void myMethod() throws ExceptionType {
    // method code
}

7.What is a custom exception in Java?

A custom exception is a user-defined exception in Java. Developers can create their own exception classes by extending the Exception class or one of its subclasses.

public class MyException extends Exception {
    public MyException(String message) {
        super(message);
    }
}

8.What is a catch block and how many catch blocks can be used with a single try block?

A catch block is used to catch and handle an exception that is thrown by the try block. A single try block can be used with multiple catch blocks, each catching a different exception type.

try {
    // code that may throw an exception
} catch (ExceptionType1 ex1) {
    // code to handle exception type 1
} catch (ExceptionType2 ex2) {
    // code to handle exception type 2
}

9.What is the base class of Error and Exception?

Throwable is the base class for both Error and Exception.

10.What is the difference between Exception and Error?

Errors are irrecoverable exceptions. Usually a program terminates when an error has occurred. Ex. MemoryOutOfBoundException.