Exception handling in Java

Exception handling is a most frequently used mechanism while developing applications in Java. There are 2 kinds of exceptions in an application:
1. at run time due to careless use of variable/return values some exception might come. This is called RuntimeException. Example of these kind of exceptions are: NullPointerException, DevideByZeroException, ArrayIndexOutOfBoundException etc.
2. During compile time, the application might throw some self defined exceptions for which we must to have either a try-catch block or throws in the method declaration. These time of exceptions are called Checked exceptions. Example of these kind of exceptions are: IOException, SQLException etc.

Exception Hierarchy

Here is the hierarchy for the Exception and Error conditions in Java.


                             Throwable
                              //           \\
                      Error              Exception
(Ex: OutOfMemory error)     //          \\
                            (Subclass: these    RuntimeException
                          are called Checked
                         Exception)


If you want to write a Exception for your own project extend the class Exception and handle the Exception in a separate Catch Block.

Example:

class BusinessException extends Exception{
...
}

void method1(){

try{

throw new BusinessException();

}catch(BusinessException be){

//enter Business exception handling logic here
}catch(IOException ioe){
//enter your exception handling logic here

}
}