Exception Handling in Java

 Exception handling

Exception handling in Java is a powerful mechanism that allows you to handle runtime errors, ensuring the smooth flow of the application. It enables a program to catch and handle exceptions gracefully, avoiding abrupt termination and providing meaningful feedback. Here's a detailed explanation of exception handling in Java:


There are two types of exception

1) System defined

2) User defined

System defined exceptions:-

In Java, system-defined exceptions are exceptions provided by the Java standard library. These exceptions are part of the java.lang package and are derived from the Throwable class. They can be broadly categorized into two types: checked exceptions and unchecked exceptions.


1. Checked Exceptions

Checked exceptions are exceptions that must be either caught or declared in the method signature using the throws keyword. They are checked at compile-time.

2.Unchecked Exceptions

Unchecked exceptions are not checked at compile-time. They are checked at runtime and do not need to be declared in the method signature or caught. These exceptions are subclasses of RuntimeException.


User defined exception:-

User-defined exceptions, also known as custom exceptions, are exceptions created by the developer to handle specific error conditions that are not covered by Java's built-in exceptions. Custom exceptions can make your code more readable and maintainable by providing more meaningful error messages and allowing you to handle specific error scenarios in a more controlled manner.


Creating a Custom Exception

To create a custom exception, you need to extend the Exception class or one of its subclasses. Typically, you'll extend Exception for checked exceptions and RuntimeException for unchecked exceptions.


Steps to Create a Custom Exception

1.Define the Custom Exception Class

2.Provide Constructors

3.Throw the Custom Exception in Your Code


Try-Catch Block

The try-catch block is the fundamental construct used to handle exceptions:

try {

    // Code that might throw an exception

} catch (ExceptionType1 ex1) {

    // Handle ExceptionType1

} catch (ExceptionType2 ex2) {

    // Handle ExceptionType2

} finally {

    // Code to be executed regardless of whether an exception is thrown or not

}


Key Components of Exception Handling

1. Try Block

Contains code that might throw an exception.

If an exception occurs, the remaining code inside the try block is skipped, and control is transferred to the appropriate catch block.

2. Catch Block

Catches and handles the exception.

You can have multiple catch blocks to handle different types of exceptions separately.

3. Finally Block

Contains code that is always executed, regardless of whether an exception was thrown or not.

Typically used for resource cleanup (e.g., closing files or database connections).

4. Throwing Exceptions

Use the throw keyword to explicitly throw an exception.

5. Throws Clause

Used in method signatures to declare that a method might throw certain exceptions.


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