Hello friends !! Today i am going to tell about
EXCEPTION HANDLING in Java ...
EXCEPTION HANDLING
The first question that we strike to our mind is what
is EXCEPTION ??
Exception: is a problem that arises during the execution
of a program.
These are following reason by which there is a
possibility to come an exception:
·
A user has entered invalid data.
·
A file that needs to be opened cannot be found.
·
A network connection has been lost in the middle of
communications, or the JVM has run out of memory.
Exception Categories :
·
Checked exceptions: A checked exception is an
exception that is typically a user error or a problem that cannot be foreseen
by the programmer. For example, if a file is to be opened, but the file cannot
be found, an exception occurs. These exceptions cannot simply be ignored at the
time of compilation.
·
Runtime exceptions: A runtime exception is an
exception that occurs that probably could have been avoided by the programmer.
As opposed to checked exceptions, runtime exceptions are ignored at the time of
compliation.
·
Errors: These are not exceptions at all,
but problems that arise beyond the control of the user or the programmer.
Errors are typically ignored in your code because you can rarely do anything
about an error. For example, if a stack overflow occurs, an error will arise.
They are also ignored at the time of compilation.
Catching
Exceptions:
A method catches an exception using a combination of the
try and catch keywords. A try/catch block is placed around the
code that might generate an exception. Code within a try/catch block is
referred to as protected code, and the syntax for using try/catch looks like
the following:
try
{
//Protected code
}
catch(ExceptionName e1)
{
//Catch block
}
A catch statement involves declaring the type of
exception you are trying to catch. If an exception occurs in protected code,
the catch block (or blocks) that follows the try is checked. If the type of
exception that occurred is listed in a catch block, the exception is passed to
the catch block much as an argument is passed into a method parameter.
Let us take an example….through
which we can easily understand how an exception may come and how we handle
that exception……..
class
abc
{
public
static void main(String[] arg)
{
int
x=10;
int
y=5;
int
z=5;
try{
int
p=x/(y-z);
}
catch(AirthmeticException
e)
{
System.out.println(“Exception”);
}
}
}
output:
Exception
class abc
{
Public static void main(String[] arg)
{
Int a[]={5,10};
Int b=5;
Try{
Int x=a[2]/a[1];
//exception come due to a[2] as this was not defined
}
Catch(ArrayIndexOutOfBoundException e)
{
System.out.println(“exception”);
}
}
}
Multiple
catch statement:
A try block can be followed by multiple catch blocks.
The syntax for multiple catch blocks looks like the following:
try
{
//Protected code
}
catch(ExceptionType1 e1)
{
//Catch block
}
catch(ExceptionType2 e2)
{
//Catch block
}
catch(ExceptionType3 e3)
{
//Catch block
}
Example
of multiple catch statement:
class
abc
{
public
static void main(String[] arg)
{
int
x=10;
int
y=5;
int
z=5;
try{
int
p=x/(y-z);
}
catch(ArithmeticException
e)
{
System.out.println(“Exception”);
}
catch(ArrayIndexOutOfBoundException
e)
{
System.out.println(“Array
range”);
}
Catch(ArrayStoreException
e)
{
System.out.println(“Array
wrong data type”);
}
}
}
output:
Exception
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