The exception handling in java is one of the powerful mechanism to handle the runtime errors so that normal flow of the application can be maintained.
In this page, we will learn about java exception, its type and the difference between checked and unchecked exceptions.
Dictionary Meaning : Exception is an abnormal condition.
In java, exception is an event that disrupts the normal flow of the program. It is an object which is thrown at runtime.
Exception Handling is a mechanism to handle runtime errors such as ClassNotFound, IO, SQL, Remote etc.
The core advantage of exception handling is to maintain the normal flow of the application. Exception normally disrupts the normal flow of the application that is why we use exception handling. Let's take a scenario:
statement 2; //exception occurs
Suppose there is 10 statements in your program and there occurs an exception at statement 5, rest of the code will not be executed i.e. statement 6 to 10 will not run. If we perform exception handling, rest of the statement will be executed. That is why we use exception handling in java.
There are mainly two types of exceptions: checked and unchecked where error is considered as unchecked exception. The sun microsystem says there are three types of exceptions:
The classes that extend Throwable class except RuntimeException and Error are known as checked exceptions e.g.IOException, SQLException etc. Checked exceptions are checked at compile-time.
The classes that extend RuntimeException are known as unchecked exceptions e.g. ArithmeticException, NullPointerException, ArrayIndexOutOfBoundsException etc. Unchecked exceptions are not checked at compile-time rather they are checked at runtime.
Error is irrecoverable e.g. OutOfMemoryError, VirtualMachineError, AssertionError etc.
There are given some scenarios where unchecked exceptions can occur. They are as follows:
If we divide any number by zero, there occurs an ArithmeticException.
If we have null value in any variable, performing any operation by the variable occurs an NullPointerException.
If you are inserting any value in the wrong index, it would result ArrayIndexOutOfBoundsException as shown below:
int a=new int;
There are 5 keywords used in java exception handling