In this article, you will learn exception handling using try-catch-finally block. In later part, you will learn using nested catch block and use of throw keyword.

Introduction

You can perform exception handling using try-catch-finally blocks, nested catch block and throw keyword. This article explains all these one by one.

Using Try-Catch-Finally blocks

There are three ways you can implement try-catch-finally blocks into your program.

1. 1) Using try-catch block
2. 2) Using try-catch-finally block
3. 3) Using try-finally block

We mostly use try-catch and try-catch-finally blocks in our program.

try{
 //Code here
} catch {
 //code here
} finally {
 //code here
}

Try Block

This block contains main business logic and error mainly encounter in this block only. You write inline code, call functions or do other stuffs in this block only.

Catch Block

Whenever a program encounter any exception, it is caught in catch block. You can catch exception in catch block, specify base Exception class to show type of error or specifically mention particular exception type to catch specific error like "DivideByZeroException".

Finally Block

This block execute in every case i.e. after execution of try block or even if encounter an error caught in catch block. We write those logic in finally block which we want to execute regardless of any condition.

Nested Try-Catch-Finally block

You can implement nested try-catch-finally block and can catch inner error under nested catch block.

try{
 //Code here
 try{
 //Code here
 } catch {
 //code here
 } finally {
 //code here
 }
} catch {
 //code here
} finally {
 //code here
}

Throw Keyword

This keyword is used to catch and throw inner exception to parent catch block. This is helpful when you want to collect all errors at one place i.e. parent catch block and handle all error at one go. This is mostly used keyword in Exception Handling.

try{
 //Code here
} catch {
//code here
 throw;
} finally {
//code here
}

Using Exception Class

In catch block, either you can simply throw error to parent block or handle in same catch block or you can customize exception like showing exception message or see stack trace using pre-defined exception class "Exception" or you can specifically use specific class like "DivideByZeroException", "NullReferenceException", "IndexOutOfRangeException" and many more.

try{
 //Code here
} catch (Exception ex){
//code here
 throw ex;
}finally {
//code here
}

Multiple Catch block

You can also multiple catch blocks to handle exceptions separately. In below example, we used multiple catch blocks. Note that you should use "Exception" class at last if you are using multiple catch blocks.

try{
 //Code here
} catch (OutOfMemoryException ex){
//code here
 throw ex;
} catch (Exception ex){
//code here
 throw ex;
}finally {
//code here
}

Hope this helps you.