This PPT gives detailed information about the Exceptions in JAVa, Types of Exceptions

1. Prepared by
V.Santhi
Assistant Professor
Department of Computer Application
Bon Secours College for Women
Thanjavur

2. • Due to design errors or coding errors, our
programs may fail in unexpected ways during
execution.
Exception
An exception is a condition that is caused by run
time error in the program.

3.  An error may produce an incorrect output or
may terminate the execution of the program
abruptly or even may cause the system to
crash. So it is our responsibility to detect and
manage the error properly.

4.  Runtime Errors: occur while the program is
running if the environment detects an
operation that is impossible to carry out.
 Logic Errors: occur when a program doesn't
perform the way it was intended
 Syntax Errors: Arise because the rules of the
language have not been followed.They are
detected by the compiler.

5. class Error
{
public static void main(String args[])
{
int a=10;
int b=5;
int c=5;
int x=a/(b+c);
System.out.println("x=" +x);
int y=a/(b-c); // Errorr division by zero
System.out.println("y=" +y);
}
}

6.  Some typical causes of errors:
 Memory errors (i.e. memory incorrectly allocated,
memory leaks, “null pointer”)
 File system errors (i.e. disk is full, disk has been
removed)
 Network errors (i.e. network is down, URL does
not exist)
 Calculation errors (i.e. divide by 0)

7.  Exceptions – a better error handling
 Exceptions are a mechanism that provides the
best of both worlds.
 Exceptions act similar to method return flags in
that any method may raise and exception should
it encounter an error.
 Exceptions act like global error methods in that
the exception mechanism is built into Java;
exceptions are handled at many levels in a
program, locally and/or globally.

8. Throwable
Exception Error
Runtime
Exception
IO Exception

9. 1. Find the problem (Hit the exception) try
2. Inform that an error has occurred (throw the
exception) throw
3. Receive the error information (catch the
exception) catch
4. Take corrective actions (Handle the
exception)

10. • Java exception handling is managed via five
keywords :
try, catch, throw, throws , finally

12.  Wrap code to be checked in a try-block
 checking occurs all the way down the execution
stack
 try-blocks can be nested
 control resumes at most enclosed matching
handler

13.  Example
 try {
… normal program code
}
catch(Exception e) {
… exception handling code
}

14.  Types of Exceptions
 Examples:
▪ public void myMethod throws Exception {
▪ public void myMethod throws IOException {
▪ try { … }
catch (Exception e) { … }
▪ try { … }
catch (IOException ioe) { … }

15. class error2
{
public static void main(String arg[])
{
int a=10;
int b=5;
int c=5;
int x,y;
try
{
x=a/(b-c);
}
catch(ArithmeticException e)
{
System.out.println(“Division by Zero”);
}
Y=a/(b-c);
System.out.println(“y=“+y);
}

16. • It is possible to throw an exception explicitly,
using the throw statement.The general form
of throw is shown here
Syntax:
throw throwableinstance;

17. • If a method is capable of causing an
exception that it does not handle, it must
specify this behavior so that callers of the
method can guard themselves against that
exception.
Syntax:
datatype method-name(parameter-list) throws
exception-list
{
body of method;
}

18. • java supports another statement known as
finally statement that can be used to handle an
exception that is not caught by any of the
previous catch statements.
• It may be added immediately after the try block
or after the last catch block shown as follows
try {
statement;
} finally
{ statement;
}